Greenwitch by Susan Cooper

the name on the boat’s stern: she was called the
White Lady.
    Merriman held the drawing at arm’s length, and released it into the sea; instantly it vanished into the shadow. There was a pause, then a soft laugh from Tethys. She sounded pleased.
    â€œSo the fishermen do not forget,” she said. “Even after so long, some do not forget.”
    â€œThe power of the sea will never change,” Will said softly. “Even men recognise that. And these are islanders.”
    â€œAnd these are islanders.” Tethys played with the words. “And they are my people, if any are.”
    â€œThey do as they have always done,” Merriman said. “They go out to the sea for fish at the going down of the sun, and with the dawn they return again. And once every year, when spring is full and summer lies ahead, they make for you, for the White Lady, a green figure of branches and leaves, and cast it down as a gift.”
    â€œThe Greenwitch,” Tethys said. “It has been born again already, this is the season. It will be here soon.” A coldness came into the voice that filtered from the shadows. “What is this favour you ask, hawk? The Greenwitch is mine.”
    â€œThe Greenwitch has always been yours, and always will. But because its understanding is not as great as your own, it has made the mistake of taking into its possession something that belongs to the Light.”
    â€œThat has nothing to do with me,” Tethys said.
    A faint light seemed to glimmer from the blue-black shadow in which she was hidden, and all around them lights began to glow and flash from the fish and sea-creatures waiting there, watching. Will saw the dangling bait-stars over great gaping mouths; strings of round lights like port-holes running thelength of strange slender fish. In the far distance he saw an odd cluster of lights of different colours, that seemed to belong to some bigger creature hidden in the shadow. He shivered, fearful of this alien element in which by enchantment they briefly breathed and swam.
    â€œThe Wild Magic has neither allies nor enemies,” Merriman said coldly. “This you know. If you may not help us, yet it is not right for you to hinder us either, for in so doing you give aid to the Dark. And if the Greenwitch keeps that which it has found, the Dark will be very much strengthened.”
    â€œA poor argument,” Tethys said. “You mean simply that the Light will then fail to gain an advantage. But I am not permitted to help either Light or Dark to gain any advantage. . . . You speak deviously, my friend.”
    â€œThe White Lady sees everything,” Merriman said, with a soft sad humility in his tone that startled Will, until he realised that it was no more than a delicate reminder of their gift.
    â€œHa.” There was a flicker of amusement in the voice of the shadow. “We will have a bargain, Old Ones,” Tethys said. “You may in my name try to persuade the Greenwitch to give up this . . . something . . . that is of such value to you. Before the creature comes to the depths, this is a matter between it and you. I shall not interfere, and the Dark may not interfere either, in my realm.”
    â€œThank you, madam!” Will said, in quick delight.
    But the voice went on, without pause, “This shall be only until the Greenwitch turns, to come to the deep sea. As it always comes, each year, to its proper home, to me . . . and after that time, Old Ones, anything that is in its possession is lost to you. You may not follow. None may follow. You may not return here, then, even by the spell which brings you here today. Should the Greenwitch choose to bring your secret down to the deeps, then in the deeps for ever it shall remain.”
    Merriman made as if to speak again, but the voice from the darkness was cold. “That is all. Go now.”
    â€œMadam—” Merriman said.
    â€œGo!” Rage filled the voice of Tethys