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 game is on, and Max and Derrick are on the case . . . but they could be headed for the deadest of ends as they battle to bag the menacing Fur Ball of the Apocalypse!