Gentle Ben

Mark befriends a boy whose family is vacationing on a houseboat in the river. While out on an adventure together a hurricane quickly comes in. They get the boy's mother from the houseboat and Ben leads them to the safety of a cave.

As Tom and Mark are watching a mother bear play with its cub the mother gets shot by a swamp hunter. Tom issues as citation to the hunter and takes the cub. Ben appears to be jealous of the cub and when the hunter's boy steals the cub Mark assumes Ben chased it off. They discover that the boy stole the cub because living in the swamp he had no friends or pets. In an on the spot judgement, Tom tells the boy that the terms of his probation are to take good care of the cub, and the boy's father goes along with it.

Ben and Mark stumble upon fish poachers and their illegal smokehouse. The men threaten to kill Ben if Mark tells his father. Later Ben wanders off and Mark follows him onto the poachers' boat; they hide but the boat takes off when they hear Tom's airboat approaching. When they start shooting at Tom, Mark and Ben come to his rescue and the poachers are arrested.

A dolphin comes up the channel and hangs around the Wedloe's dock. He and Ben become friends and Mark considers him his pet. Mark is disappointed when he finds out that the dolphin escaped from Miami Seaquarium and has to go back before he is lured by the wild dolphins at sea in mating season. The lure of mating season is too strong for the dolphin, Marco Polo, and he heads to sea with Ben following.

Mark is despondent as he has not just lost his new pet, Marco Polo, but his old pet Ben. Frank from Seaquarium takes Mark and Tom out on a boat to find Ben and Marco Polo. They spot Ben on a small island and as they get his attention and he swims for the boat he is threatened by a shark. Marco Polo comes to the rescue and nudges the shark away from Ben. Ben climbs a ladder to get onto the boat, and Marco Polo is returned to Seaquarium.

After Mark has a series of mishaps that soil three pairs of Tom's pants, Tom is angry at him. Feeling unwanted, Mark moves in to Ben's shed. While fishing, a fisherman comes by the river and hires Mark as his guide. The small boat overturns at a rough spot in the river and Mark and Mr. Carter are threatened by alligators and a cougar. Tom hears the commotion and scares off the alligators while Ben scares off the cougar. Mark and Tom have a heart-to-heart conversation and clear the air between them.