It was not dark at the entrance to the Cavern of the Sea-Woman, for the moonlight moved within it as the hand of a blind man groping blankly in an unfamiliar place. The arch of the rock was clear, and even the frondage of fern and sea-plants suspended from its lower curve; also, beneath, a mass of mossed crag, just beyond the highest reach of the tides. Among this dark crag-vegetation grew strange plants; but none stranger or so rare as the sea-grape, or mermaid's-fruit of the islanders. No one on Innisròn knew its proper designation, and it had become known at all as the sea-grape only because some student of rare things discovered and wrote about it under that name, as perhaps the culminating treasure-trove of the botanist in the Scottish West. It is a plant which clings as a tendril, choosing only the summit of high rocks or boulders in some sunless place where it can breathe the ooze from dead or dying sea-weed, and can feel the salt air reach it with a chilly touch. It lies low, with its thin, moist, ash-grey stems; its round, pale-green, transparent leaves faintly spotted with livid blotches; and its infrequent clusters of small, juicy berries of a hue of dusky yellow.
The isle-folk regard it with awe. Though the fruit is poisonous, and a deadly draught can be distilled from the leaves, a few berries would not suffice to kill. To eat sparingly of the sea-grape is not to invite death necessarily, but to bring about a stupor so deep that for an hour or more no familiar sound can reach the ear, no ordinary shock vibrate along the nerves, no common pain affect the body. If the eater of the mermaid's-fruit be left undisturbed, he will not stir for twelve or even fifteen hours, though the first death-like trance does not prevail beyond an hour, or at most two: while, if forcibly aroused, he is so weak in body and so dazed in mind that he cannot long be kept awake without peril to the brain, and indeed to life itself.
It was because of this fruit of oblivion that Alastair and Lora had sought the Cave of the Sea-Woman.
They had feared not so much their own instinctive evasion of death as that, in the final struggle, they might not go down into the shadow together.
The idea that the Silence should come upon them unawares--that, arms about each other in a last embrace, the wave should encroach upon their deep unheeding slumber--had given them a strange elation. The thought was Alastair's. Though he was not a native of Innisròn, he had often visited it from Dunvrechan even before he had come to love Lora, and was familiar with each of the treacherous caves and all the desolate, boulder-strewn, uninhabited south-western side of the island, as well as with everything in animate or inanimate nature which was to be found therein. Not only had he often heard of the sea-grape which grew almost inaccessibly in some of the caverns on the western side, but he knew where in the Cave of the Sea-Woman it was to be obtained with little difficulty.