A group of scientists travels to the Amazon jungle at the behest of Dr. Thorkel, a reclusive and eccentric biologist seeking assistance with his experiments. Upon their arrival, they discover Thorkel has been investigating the properties of radium and its transformative effects on living organisms. Thorkel's increasing paranoia and secretive behavior raise suspicions among the group as they notice animals displaying unusual characteristics. Their fears are confirmed when Thorkel reveals his true intentions: he has found a way to shrink living beings to a fraction of their original size. Caught off guard, the scientists realize they must find a way to escape this madman's grasp before becoming permanent subjects of his experiments.

As tensions escalate, the scientists begin to plot against Thorkel, but their diminutive size makes even the simplest tasks perilous. They navigate a treacherous environment where everyday objects become colossal obstacles, and dangerous creatures pose even greater threats. Determined to survive, they must utilize their collective knowledge and skills to outwit Thorkel and secure their return to normality. Throughout this harrowing ordeal, the scientists build alliances and uncover hidden truths about Thorkel's motives and past. Their resilience and ingenuity are tested as they engage in a desperate struggle for freedom against a brilliant but deranged opponent.