One late summer day in 1961 a biologist named Sherman Bleakney got a telephone call about a strange sea creature that fishermen had just unloaded on a wharf in Halifax, Nova Scotia. Bleakney, who lived nearby, was captivated by what he found there. Sprawled on its back amid a curious crowd was an immense black sea turtle tipping the scales at 900 pounds, with a soft, rubbery carapace, winglike front flippers, and a massive, conical head like an artillery shell. Bleakney recognized it as a leatherback, the biggest of all sea turtles. Leatherbacks, he recalled, were supposed to be creatures of the tropics, as out of place in chilly, gray Canadian waters as parrots in a Halifax park.