Upon the death of his beloved Uncle Calvin, a young Jonah Padgett makes his way to Sag Harbor with nothing but a letter of introduction and a strange amulet shaped like a dolphin. He signs on to the whaler Absalom, under the command of his uncle’s old friend, Captain Solomon. Upon rounding the Horn, the crew hears stories of a sperm whale said to be as big as a mountain with skin as black as a bible, and in command of a harem of a hundred females. Captain Solomon wagers that his crew will be the one to make its fortune hunting down the elusive King Jim . But when the Absalom signs on the native called Koro as a harpooner, the ship is beleaguered by inexplicable disappearances and horrific death, which pits shipmate against shipmate. While trying to clear his friend of suspicion, Jonah finds himself adrift in a fantastical world filled with dolphin-like merfolk and nightmarish were-sharks, endangered equally by inhuman creatures from the ocean’s depths and human fear and superstition, his very life at the mercy of something as old and mysterious as the sea itself.