Eager to be of help, Ian put off in his boat, and was soon among the fishermen, who in their new excitement were forgetful of all else than that the mackerel were come, and that every moment was precious. For the first time Ian found himself no unwelcome comrade. Was it, he wondered, because that, there upon the sea, whatever of shadow dwelled about him, or rather about Alan MacAilean, on the land, was no longer visible.

All through that golden noon he and the others worked hard. From isle to isle went the chorus of the splashing oars and splashing nets; of the splashing of the fish and the splashing of gannets and gulls; of the splashing of the tide leaping blithely against the sun-dazzle, and the illimitable rippling splash moving out of the west;—all this blent with the loud, joyous cries, the laughter, and the hoarse shouts of the men of Barra and the adjacent islands. It was close upon dusk before the Rona boats put into the haven of Aonaig again; and by that time none was blither than Ian MacIain, who in that day of happy toil had lost all the gloom and apprehension of the day before, and now returned to Caisteal-Rhona with lighter heart than he had known for long.

When, however, he got there, there was no sign of Alan. He had gone, said Giorsal, he had gone out in the smaller boat midway in the afternoon, and had sailed around to Aoidhu, the great scaur which ran out beyond the precipices at the south-west of Rona.

This Alan often did, and of late more and more often. Ever since he had come to the Hebrid Isles his love of the sea had deepened and had grown into a passion for its mystery and beauty. Of late, too, something impelled to a more frequent isolation, a deep longing to be where no eye could see and no ear hearken.

So at first Ian was in no way alarmed. But when the sun had set, and over the faint blue film of the Isle of Tiree the moon had risen, and still no sign of Alan, he became restless and uneasy. Giorsal begged him in vain to eat of the supper she had prepared. Idly he moved to and fro along the rocky ledge, or down by the pebbly shore, or across the green àiridh, eager for a glimpse of him whom he loved so well.

At last, unable longer to endure a growing anxiety, he put out in his boat, and sailed swiftly before the slight easterly breeze which had prevailed since moonrise. So far as Aoidhu, all the way from Aonaig, there was not a haven anywhere, nor even one of the sea caverns which honeycombed the isle beyond the headland. A glance, therefore, showed him that Alan had not yet come back that way. It was possible, though unlikely, that he had sailed right round Rona; unlikely, because in the narrow straits to the north, between Rona and the scattered islets known as the Innsemhara, strong currents prevailed, and particularly at the full of the tide, when they swept north-eastward dark and swift as a mill-race.

Once the headland was passed and the sheer precipitous westward cliffs loomed black out of the sea, he became more and more uneasy. As yet, there was no danger; but he saw that a swell was moving out of the west; and whenever the wind blew that way, the sea-arcades were filled with a lifting, perilous wave. Later, escape might be difficult, and often impossible. Out of the score or more great passages which opened between Aoidhu and Ardgorm, it was difficult to know into which to chance the search of Alan. Together they had examined all of them. Some twisted but slightly; others wound sinuously till the green, serpentine alleys, flanked by basalt walls hundreds of feet high, lost themselves in an indistinguishable maze.

But that which was safest, and wherein a boat could most easily make its way against wind or tide, was the huge, cavernous passage known locally as the Uaimh-nan-roin, the Cave of the Seals.

For this opening Ian steered his boat. Soon he was within the wide corridor. Like the great cave at Staffa, it was wrought as an aisle in some natural cathedral; the rocks, too, were columnar, and rose in flawless symmetry, as though graven by the hand of man. At the far end of this gigantic aisle, there diverges a long, narrow arcade, filled by day with the green shine of the water, and by night, when the moon is up, with a pale froth of light. It is one of the few where there are open gateways for the sea and the wandering light, and by its spherical shape almost the only safe passage in a season of heavy wind. Half-way along this arched arcade a corridor leads to a round cup-like cavern, midway in which stands a huge mass of black basalt, in shape suggestive of a titanic altar. Thus it must have impressed the imagination of the islanders of old; for by them, even in a remote day, it was called Teampull-Mara, the Temple of the Sea. Owing to the narrowness of the passage, and to the smooth, unbroken walls which rise sheer from the green depths into an invisible darkness, the Strait of the Temple is not one wherein to linger long, save in a time of calm.

Instinctively, however, Ian quietly headed his boat along this narrow way. When, silently, he emerged from the arcade, he could just discern the mass of basalt at the far end of the cavern. But there, seated in his boat, was Alan, apparently idly adrift, for one oar floated in the water alongside, and the other swung listlessly from the tholes.