Young Chris Carlyle lives with his parents, Adam and Anne, on a ranch where he has made friends with a mountain lion cub. When the Carlyle family moves to a small town, Chris is told that he must leave his pet behind, but the lion hides in the trailer and arrives with the family. Upon discovering the stowaway, Chris's father finally persuades the boy to give the lion to a local zoo. Dr. Del Hartwood, the superintendent, and Branch Hawksbill, the zoo keeper, are friendly; but the zoo is crowded and Chris feels sorry for the animals caged there. One day Chris picks up the zoo keeper's keys and frees his lion as well as the rest of the animals. The animals run rampant with their new freedom; lions, hippos, elephants, monkeys, and zebras romp through the town and into the homes of the people. Hartwood and Hawksbill manage to round them all up before the police can shoot them, and the town finally awards the zoo much-needed funds for improvements.
