Love, loss and competitive tree-climbing are preoccupying the hero of ''Coelacanth''. This is a boy-meets-girl story with a twist, a tumble, several daring somersaults from the branches, and the discovery that love - like the coelacanth fish that was thought to be extinct - can lurk in the very darkest depths. In ''Not Everything Is Significant'', we meet a biographer who is suffering from writers'' block and a footnoter who is a stickler for detail - together they''re pondering the meaning of a diary that arrived mysteriously through the post and which appears to predict the future, prompting some very tricky questions about the nature of destiny. Finally, in ''Supercollider for the Family'' a husband and wife each face a challenge: he to build a ''supercollider'' small enough for household use, she to complete a tightrope walk around the world. Their missions take us from a top-secret particle-physics lab deep underground to the vertiginous heights of a wire above a canyon, suspended like a slender silver thread between soil and sky. Originally written for stage performance, laced with wit and bursting with imagination, these three disarming creations work a dazzling, moving magic on the page.