It's the middle of the thirteenth century in the little riverside village of Crundall. For 16-year-old orphan Jack Fisher, it's one of the best times of the year, for the Fair of St Thomas is in full swing, and this year, the most extraordinary creature ever captured is being displayed: a merman. Jack has come prepared to stare and goggle with the others, but there's something about this creature that affects Jack most strongly. Perhaps it is because he himself has been born with webbed toes on one foot, and knows full well how cruel people can be with their teasing . . .
Late that night, Jack creeps down to the place where the merman is kept. And it is then that he gets the shock of his life, for the merman speaks to him. Placing a chain around his neck - the chain of Glasmor - the merman tells Jack that he is, in fact, kin of the water-folk and that the Green Prince is calling him to save the underwater world from Grimlow, the Silver Shadow of the Abyss, the Monster of Darkness. The challenge seems preposterous to Jack, but at the same time something deep down tells him it's what he must do . . .
