While trying to steal the Keeper’s ship, Dr. Smith accidentally releases all of the Keeper's specimens. Smith is frightened by the animals and runs back to the Jupiter 2 and he orders the Robot to erase the incident from his memory banks. Later on, John and Don encounter some of the more dangerous animals and are forced to destroy some. They cannot understand why the Keeper should have released his animals and Don suspects Smith was probably responsible. The Keeper, furious, comes to the Jupiter 2, determined to discover who was responsible. When Smith is revealed to have been responsible, the Keeper demands reparation from the Robinsons since many of his specimens have been killed; the Robinsons must surrender Will and Penny to him. John and Maureen naturally refuse, but the Keeper warns