Derrick's goldfish friends, Finn and Gillian, have gone missing Things take a turn for the weird when Derrick realizes his two science teachers are also nowhere to be found. Is it possible Finn and Gillian have been transformed into giant teacher-snatching zombie-robot piranhas? Could mysterious postcards hold the answers? And what do plankton, plastic, and the fate of the oceans have to do with missing persons and punny, piscatorial pets? The...