exactly three weeks after the capture of the mendez nunez the alerte arrived off the mouth of the wad-el-abuam, a small river flowing into the atlantic a few miles south of cape bojador.

the estuary formed an ideal base for captain cain's new sphere of operations. nominally within the limits of rio del oro—spain's extensive, unproductive and loosely-held dependency, stretching from morocco on the north to french senegal on the south—the wad-el-abuam was hardly ever visited by vessels, except moorish coasters and fishing craft.

the entrance to the river was a difficult one, a bar on which the surf broke heavily, extending practically right across it, although well on the starboard hand was a narrow channel carrying twenty feet at high water and protected by a long, narrow rocky island that not only served as a breakwater, but also effectively screened the estuary when viewed from seaward.

within the bar the depth increased to sixty feet, with a bottom of firm white sand. farther up, the bed was composed of mud that became more objectionable as the width of the river decreased. the banks were almost destitute of vegetation, consisting of sand with a few palms and a scanty scrub that afforded meagre food for goats belonging to the inhabitants. there were four or five small villages populated by a tribe of savages, half arab, half negro, who had long resisted any attempt at subjection on the part of the spanish troops stationed at villa cisnero and other fortified posts of rio del oro.

within two hundred miles lay the canary islands, with funchal, the favourite port of call for ships running between europe and the west and south coasts of africa. farther to the south'ard was teneriffe, with las palmas, another frequented coaling-station. both these were within the alerte's wireless radius, so that the pirates hoped to obtain a fairly complete report of all vessels passing within striking distance of their proposed base.

"i suppose we haven't made a mistake," remarked pengelly, as the alerte slowly approached the land. "i can't see any sign of an estuary."

"it must be there," replied cain, after consulting the latest but far from reliable chart of this part of the coast. "we'll stand in a bit more. if there's any doubt about it, we'll send a boat and take soundings. the sailing directions state that the island is hardly distinguishable from the mainland except at short distance."

he levelled his binoculars for the twentieth time during the last hour.

"by thunder!" he exclaimed. "hanged if there isn't a sail coming round the point. native craft, by the cut of her."

"that's awkward," remarked the second in command. "we don't want company of that sort. she's heading towards us."

"let her," said cain, with his characteristic grim smile. "let her. mr. marchant, serve out the small arms. get up the machine-gun, but keep it out of sight until it might be wanted. we'll nab that fellow and make the crew pilot us in."

little guessing what reception awaited her, the boat approached. she was a roughly-built craft of about thirty feet in length, bluff bowed and with a high, ungainly stern. her rig resembled that of a felucca, but with a boom in place of the loose-furled sail usually affected by craft of the type to be met with in the mediterranean. it could be seen that there were three men on board. one, dressed in a loose garment of white, including a burnous, was at the long, curved tiller. the others, darker skinned, wore loincloths only.

while the alerte was yet a quarter of a mile from her, the felucca ported helm, close-hauled, and stood off in a nor' nor'-westerly direction.

"what's her little game, i wonder?" remarked pengelly. "i thought she was coming off to us."

"so did i," agreed captain cain. "but now i think she's a moorish fishing vessel homeward bound. she had to stand out towards us to avoid running on the shoals. we'll collar her, pengelly. if the old boy in the cotton nightgown is reasonable we'll pay him and let him go when he's piloted us in."

in obedience to an order from the bridge, the alerte's diesel engines slowed down, till at a modest three and a half knots the pirate submarine gained position between the felucca and the shore. having thus cut off the latter's retreat, the alerte starboarded helm and, working up to twelve knots, began to overhaul the native craft with ease.

a cast of the lead gave nine fathoms, and since the chart showed that the soundings were remarkably even on this course, captain cain had no apprehensions of running his vessel aground.

the crew of the felucca seemed quite apathetic when they saw the alerte in pursuit. at a sign from the white-robed moor the two blacks lowered the sails, one of them standing by to heave a line.

declutching her propellers, the pirate submarine gradually lost way, coming to a dead stop alongside the felucca.

by means of a conversation conducted chiefly by signs, captain cain imparted his request for a pilot, and without the faintest display of hesitancy the moor scrambled on board the alerte, leaving his two men to drop the felucca astern. nor did he betray any sign of fear when he saw the pirate crew armed with automatic pistols. calmly, and in a dignified manner, he proceeded to find out the draught of the ship. this he did by producing a piece of cord about a yard in length and then drawing the rough profile of a steam vessel. with a much smaller piece of string he then measured off the draught on his plan, and then pointing first to the longer cord and then to the alerte he managed to make his meaning clear.

captain cain replied by indicating the longer cord and then holding up six fingers. the moor nodded gravely and motioned to the pirate skipper to order the ship to forge ahead.

slowly the alerte made her way inside the island, and thence through the channel over the bar. the while the lead was kept going, pengelly and the bo'sun taking bearings and noting how the channel bore for future occasions.

"stand by and let go!" roared cain as the alerte arrived at her anchorage. "is the buoy streamed, mr. barnard?"

"ay, ay, sir!" replied the bo'sun.

"then let go!"

with the rattle of chain tearing through the hawsepipe, the anchor plunged to the bed of the wad-el-abuam.

pengelly turned to his captain.

"snug little crib, this, sir," he remarked. "what about our pilot? are we going to overhaul his boat in case there's anything useful? the blighter might have been pearling. one never knows."

"certainly not," replied cain, with a deep frown of disgust. "the fellow did us a good turn. only an ungrateful, low-down swine would suggest such a thing."

turning to the moor, who was standing a couple of paces off, the pirate captain handed him a gold coin.

the pilot took the piece of money, made an elaborate salaam, and went to the side, the felucca having been brought to the gangway. already the two negroes were hoisting sail. with another salaam, the moor boarded his own craft, the ropes were cast off, and the felucca headed for the open sea.

directly the intervening island hid the anchorage, the hitherto grave features of the pilot were suffused with a broad grin.

"start up the motor, tom!" he exclaimed in english. "george, send the aerial aloft. by jove! i had the wind up when that pirate bloke suggested overhauling the boat!"

in quick time the aerial was spread between the two masts and the "lead-in" connected to a powerful wireless set concealed between double bulkheads at the after end of the little fo'c'sle. a message was then dispatched in code to the officer commanding h.m.s. canvey, giving the position of the pirate submarine's new base.

it was a smart bit of work. the canvey, formerly a tramp steamer, had been fitted out by the admiralty as a decoy-ship, disguised as the belgian passenger and cargo boat candide and supposed to be running between borna, in belgian congo and antwerp. commanded by lieutenant-commander ralph raxworthy, d.s.o., she was armed with six six-inch guns and two submerged torpedo tubes, while for scouting purposes she carried in her hold two of the latest type of small flying boats fitted with folding wings. these aircraft could be hoisted out and ready to ascend within the space of twelve minutes.

but in order to locate the alerte's base without exciting suspicion or giving any indication of her presence in the offing, raxworthy had applied for seven boats of a type in use on this part of the coast. each of these was fitted with a paraffin motor and a wireless installation, and was placed in charge of either a junior commissioned officer or else a warrant officer. for crew, west indian negroes with a good knowledge of being able to manage a boat under sail, were enlisted for temporary service, two or three being told off to each boat.

it was a job that sub-lieutenant gerald broadmayne would have given much to have undertaken; but in his case the risk was too great. not on account of possible personal danger was he turned down. in spite of a skilful disguise he might be recognised by captain cain, should the two meet. in that case the pirate would realise that a british warship was hard on his heels and would take precautions accordingly.

well before sunset the seven tenders, recalled by wireless, returned to their parent ship. almost the first to arrive was the boat commanded by sub-lieutenant allerton, who had served under raxworthy in the windrush when she claimed to have sunk the alerte in st. ives' bay.

allerton was in high feather. it was he who had "trailed the tail of his coat" across the path of the pirate submarine and had piloted her into the estuary of the wad-el-abuam.

"cain, as he calls himself, is rather a sport," he declared to his rather envious brother-officers. "but that fellow pengelly is an out-and-out rotter—a cross between a broken-down mummer and pickpocket. you know the type i mean."

"how is cain a sport?" inquired the torpedo lieutenant.

"he ticked the mealy-mouthed blighter off when he suggested helping himself to whatever he could find in the boat," replied allerton. "cain jumped on him properly, and gave me a german ten-mark gold-piece as a sort of backsheesh. he'd probably pinched it. i didn't ask questions. i'll have the thing made into a brooch when we get home."

lieutenant-commander raxworthy did not receive the information of the pirate submarine's base with any degree of enthusiasm. in fact, he was rather down in the mouth about it. he had hoped that the alerte would seek shelter in an obscure port in morocco. then the canvey could go in and settle with her. the fact that the wad-el-abuam was in spanish territory, however loosely held, complicated matters considerably. without violating international law he could do nothing unless the spanish government agreed to allow the british warship a free hand.

accordingly, the canvey put into teneriffe and reported to the admiralty by cable lest a lengthy dispatch by wireless, even though it were in code, should alarm the pirates and prompt them to change their base.

for the next few days the decoy ship steamed to and fro between the canaries and st. vincent sending out fictitious messages en clair in the hope that the alerte would emerge from her retreat and come outside the three-mile limit in order to seize a likely prey. but no alerte put in an appearance.

meanwhile, the spanish government had refused to accede to the british admiralty's request. since the pirate vessel had made use of a harbour in a spanish colony, it was "up" to spain to avenge the insult to her national dignity. accordingly the destroyer villamil was ordered to leave cartagena and proceed to wad-el-abuam to destroy the alerte.

the villamil was an old vessel of three hundred and sixty tons, with a speed of twenty-eight knots. her armament consisted of five six-pounders, of which three could fire ahead and three on the beam. in addition, she carried two torpedo tubes.

while the spanish destroyer was speeding south, the alerte remained riding to her anchors in wad-el-abuam. it was not owing to inclination on the part of captain cain that she did not put to sea. wireless messages were frequently being intercepted from vessels bound to and from the french and belgian colonies on the west coast of africa. tempting prizes they appeared to be. but the alerte had developed a leak where the post of the vertical rudder passes through the trunk. a gland had given out. it would have been a fairly simple business to effect repairs could the submarine be dry-docked. in present circumstances it was a tedious and difficult process, and until it were completed the alerte would be unable to submerge without the almost certain result of being flooded. while on the surface the leak could be kept under control; but at any great depth the hydrostatic pressure would be irresistible.

while this work was in progress, captain cain had not allowed other matters to slide. one of his first steps was to establish a signal station on the rocky island guarding and screening the alerte's anchorage. day and night armed men were on watch at the station, ready to signal to the pirate vessel the moment any sail appeared over the horizon.

just before noon one morning, captain cain was informed that a craft looking like a destroyer was approaching from the nor'ard and steaming a course parallel to the coast.

although fully conscious of the danger the alerte was incurring by being caught in a disabled state, captain cain showed no sign of panic. he was trapped. he knew it. unable to submerge, unable to ascend the river more than a few miles with a draught that considerably exceeded that of a destroyer, he realised that the only thing to be done short of scuttling the alerte and chancing a doubtful refuge ashore in a barren country inhabited by fierce natives, was to fight it out.

in hot haste six men with the machine-gun were sent off in a boat to the island with instructions to keep under cover and not to open fire until the approaching destroyer came within a hundred yards of the rock, which she must do by reason of the tortuous course of the deep-water channel.

the alerte was swung athwart the river to enable her six-inch quick-firer to bear. with the exception of the captain, mr. marchant and the gun's crew, all the rest of the hands were ordered below to be ready to replace casualties amongst the men working the quick-firer.

presently a signal came through from the island: "destroyer holding on. is flying spanish colours."

"in that case we needn't worry much, my lads," exclaimed cain. "she's probably going down the coast. if she isn't, then we're more than her match. there's not a single destroyer belonging to the spanish navy with a gun anything approaching our six-inch. we'll give it her in the neck if she tries conclusions with us."

after a brief interval, another message came through: "destroyer turned eight point to port and is making for the bar."

"good enough, my hearties!" declared cain in his ringing, convincing voice. "let her have it directly she pokes her nose round the bluff. what's the opening range, mr. marchant?"

"two thousand yards, sir," replied the gunner.

under the captain's orders one of the crew ran off with a bundle under his arm. presently a flag was hoisted at the ensign staff. for the first time the alerte was showing her true colours—the "jolly roger."

alone on the bridge, cain stood calm and confident. there was not the slightest tremor in his large, powerful hands as he grasped his binoculars ready to bring them to bear upon the as yet invisible enemy.

from his elevated position he gave a rapid glance at the gun's crew. the men had closed up round their weapon, the gunlayer bending as he peered through the sights. in the rear crouched the loading-party, each with his hands on a hundred-pound projectile, ready the moment the breech-block was opened to thrust the shell into the still smoking breech. and somehow cain's thoughts flew back to a similar scene in the presence of an enemy. then, he was fighting for a just cause under the glorious white ensign. now, he was fighting for no cause but his own, his hand against every man's, and under the shadow of that emblem of dishonour—the skull and cross-bones.

round the precipitous face of the island appeared the lean bows of the spanish destroyer. then her round bridge, mast and funnels came into view. through his glasses cain saw that her fo'c'sle gun was manned by a crew of white-clad, swarthy-faced men.... there was a deafening crash as the alerte's six-inch sent the hundred-pound projectile hurtling on its way.... even as he looked, cain saw a vivid flash immediately in front of the destroyer's bridge... a cloud of smoke torn by diverging blasts of air.... the smoke dispersed, or rather the destroyer's speed carried her through it.... the crew of her fo'c'sle six-pounder had dispersed, too; with them the gun and its mounting.... the bridge didn't look the same as it had a few seconds previously—a bit lopsided. flames were pouring from a heap of débris in the wake of the foremast.

at two thousand yards the appalling noise caused by the explosion of the alerte's first shell was inaudible to the solitary watcher on her bridge. the scene brought within a very short distance through the lenses of the powerful binoculars resembled a "close-up" picture on the cinematograph—unrealistic by reason of the absence of sound.

two vivid flashes leapt from the spanish destroyer's deck, one on the port side, the other to starboard. they were her reply to the destructive "sighting shot" from the pirate submarine.

the villamil had received a rough awakening. her crew, not one of whom had previously been under fire, were lacking in that courage and tenacity that marks the anglo-saxon race. appalled by the havoc wrought on the fo'c'sle, the gunlayers of the remaining weapons that could be brought to bear certainly did make reply. their aim was bad. one shell whizzed high above the alerte's masts, shrieking as it sped to bury itself harmlessly in the sand three miles away. the other, striking the water a hundred yards short of its objective, ricochetted and hurtled through the air full fifty yards astern.

cain paid no attention to either. his interest was centred upon his attacker. he could hear the rapid crashes of the alerte's quick-firer. he could see the results by the frequent lurid bursts of flame and the showers of débris as shell after shell struck the luckless spaniard.

still she came on, leaving an eddying trail of smoke. one of her six-pounders was firing spasmodically. she was reeling like a drunken man.

suddenly cain put aside his glasses and made a spring for the telegraph indicator, moving the starboard lever to "full ahead." his quick eye had discerned a glistening object curving over the villamil's side. a torpedo was already on its way, travelling at the speed of a train in the direction of the pirate submarine.

well before the action the alerte's oil-engines had been started with the clutches in neutral position. it was a precaution that was justified in its results. under the action of one propeller only the alerte forged ahead, her stern swinging round as she overran her anchors.

cain had no occasion now to use his binoculars. the double diverging wake of the submerged locomotive torpedo was plainly visible to the naked eye. it was approaching very rapidly; the ship was swinging very slowly—too slowly, it seemed.

for ten seconds the captain held his breath. looking aft, the rise of the poop intercepted the wake of the torpedo. it seemed as if the alerte was doomed.

but no explosion tore her asunder. by less than a couple of yards the deadly missile cleared her stern, to detonate harmlessly against the steep bank of the river half a mile away.

the alerte's quick-firer was now silent. the manoeuvre that had saved her from the torpedo had brought her almost bows-on to the villamil, with the result that the former's fo'c'sle masked her line of fire.

by this time the spanish destroyer had closed to about a thousand yards. she was yawing badly. possibly her steam-steering gear had been demolished and she was being conned from aft. nevertheless, she was keeping to the channel which at this particular time brought her almost abeam. her decks were a shambles, two of her funnels had disappeared. the rest of the bridge that had survived the alerte's first shell had collapsed. one gun well aft alone was spitting defiance. either she meant to ram her anchored opponent, or else she was manoeuvring for a position favourable for the release of a second torpedo.

again the alerte's engine-room telegraph bell clanged. with the port propeller going hard astern, and her cables tautened like harp-strings, she began to swing into her former position.

for the first time since the action commenced captain cain spoke. leaning over the bridgerail he shouted to the gunlayer to aim for the spaniard's aft torpedo-tube.

the villamil was well down by the head and had a pronounced list to starboard. her speed had appreciably fallen off. the menace of being rammed was now hardly worth taking into account; but the torpedo—— at that range, if the spanish torpedo-gunner knew his job, it was almost a matter of impossibility to miss.

cain could see four or five grimy figures bringing the loading cage to the after-end of the tube. the torpedo was launched home.... he could see the convex metal cover swing into the closing position... the torpedo coxswain was getting astride the tube... in another three or four seconds...

a deafening crash told the anxious skipper of the alerte that the six-inch was again at work. at a range of six hundred yards the shell got home. a terrific flash—it was far too vivid for the explosion of a shell—leapt from the destroyer. an enormous cloud of smoke was hurled skywards, completely obliterating the villamil from cain's vision. a blast of hot air swept over the superstructure of the submarine. pieces of metal tinkled on her steel deck. heavier pieces were falling with a succession of splashes into the smoke-enshrouded water.

slowly the pall of acrid-smelling vapour dispersed. where the destroyer had been was an expanse of agitated water surrounding a broad and steadily-growing patch of black oil. of the eighty men who formed her crew, not one survived.

the only casualty on board the alerte was no. 3 of the gun's crew, and he had been knocked out only after the villamil had been destroyed. a fragment of steel descending with terrific force had struck him on the head, killing him instantly.

the action over, captain cain brought the rest of the hands on deck.

"my lads!" he exclaimed, "if we were out for glory, we've got it. it wasn't of our seeking. it's riches, not glory, we're after. now, lads, although there's no one of our opponents left to tell the tale, we'll have to get a move on. one more good capture and we pay off. with luck we'll finish repairs by nightfall. to-morrow i hope our aims will be realised. there's a belgian vessel due to leave st. vincent at dawn to-morrow. she's ours for the asking. i propose to capture her and bring her in here until we can unload everything of value. all then that remains to be done is to hide the booty, make our way home and come out again as quite above-board west coast traders. that's all i have to say, lads. no hanging on to the slack, but plenty of beef into your work for the next few hours and everything will be plain sailing. pipe down!"