Dorrie steals Flipper and sells him to a carnival owner.

Porter is concerned that Bud is taking old Hap Gorman's stories too seriously and warns his son that not everything the old man tells him is true.

While Sandy and Bud prepare for the annual Coral Key Park swimming race, Porter is overcome by toxic chemicals dropped from a passing ship while he is carrying out an underwater investigation.

Bud trying to help an injured man and his wife marooned on a sailboat, has to call desperately for help from Flipper when the boat becomes caught in treacherous coral reefs.