Inspired by the pending war games scheduled for a nearby fort, Timmy, Boomer and friends play soldier and wander into a dangerous part of the maneuver area.
When Ruth has a flat tire, she chases her runaway spare tire into woods where she becomes caught in a holding trap placed by the state to capture a cougar forced into the area by a fire.
For a club project, Timmy and Boomer adopt a century old apple tree that is to be removed for the construction of a highway but the tree is saved for transplant in the Martin orchard when Timmy writes the President.
When Lassie continues to come home greasy, a pool of oil is discovered in the flax field which causes the Martins to dream of riches until Paul discovers a broken refinery pipeline.
An itinerant handyman fakes accident and injury and surreptitiously creates disrepair on the Martin farm to gain food and lodging which actions fool everyone except Timmy and Boomer.
When Lassie is found to be possibly descended from a very successful line of show dogs, Timmy is instructed on a regime to prepare Lassie for shows but the regime strains his friendship with Boomer.
Despite warnings by Lassie and Timmy, the rest of the Martin's believe a devious cat that feigns injury and fakes pest control behavior while creating mischief is a special animal.
Timmy and Boomer are disappointed when they find out that Lassie puppies are to be sold, meanwhile Lassie hide her pups in the woods to delayed the sale.
When Lassie is left at a neighbor while the Martins are at the country fair, the neighbor's pet chimpanzee causes havoc in their home which Lassie is blamed for.
Timmy and Boomer heartily disagree over the methods and tasks involved in the construction of a lean to but learn to work together when the boys and Lassie must rescue Boomer's visiting cousin Millicent from a cave ledge.
Lassie befriends a stray dog and finds a rambunctious runaway show horse which, after Lassie trains the stray dog to be a stable mate, becomes more calm.
Timmy wants his school to participate in The Lone Ranger Peace Patrol program encouraging children to save their money to buy saving bonds to support the United States.
An unprepared city boy who has after a quarrel run away from his uncle with whom he is visiting leads Timmy and Boomer who are camping out in the Martin barn into danger in the woods.
When Boomer goes on an overnight visit, Mike who has been left in Timmy's care becomes shut in the trunk of the Martin's car while chasing his ball and taken to a garage where a fire starts.
The Martins replace their icebox with a brand new second hand electrically operated refrigerator which is a change to which Lassie has trouble adjusting.
When Willie tells Timmy about contest for circuit tickets for letters about best pet, Timmy writes a letter on the last day and gives it to Lassie to post but it is made undeliverable when Lassie has to help Willie, Mr. Burke and Mr. Huff.
Roy Campanella arrives in town to instruct the Calverton boys' baseball team during which one of the boys uses threats and bribery to be pitcher and leaves Timmy in a conundrum as to what his action should be in the situation.
The Martins house a man and his horses, one fast and the other lazy, prior to a sulky race at the county fair and when the fast one becomes lame, the man must use the lazy one but Lassie has trained the lazy one to run.
When Timmy gains respect for his courage by keeping pace with a much larger peer in a fight and is asked by the boys to play football, Ruth has difficulty accepting this as part of the growing process.
A foreign exchange student's confession of stealing from Timmy's classmates because of her family's hunger inspires the class to help Ruth in her task as a coordinator for UNICEF.
When the Martin farm runs short of water, Paul hires a geologist to help after refusing Cully Wilson's help with a divining rod which he gives to Timmy who finds a spot that a driller chooses after the first drilling fails.
Timmy has developed the habit of telling tall tales which leads him to befriend a senior woman he has identified as a witch but his habit causes his displeased parents not to believe him when the woman needs help.
Timmy believes he has seen a space alien and food is frequently disappearing from Ruth's kitchen but the culprit is a chimpanzee loose from college experiments.
When Paul is unable to get a neighbor to hospital in time, the Martins realize the need for a closer emergency hospital for which banker/farmer Blalock's land is perfect but Blalock is stubbornly resistant to the idea.
Timmy is locked in a woodshed while selling newspaper subscriptions he discovers that new neighbor Vance is being threatened by a prison mate with exposure of his record as and force to rob the safe at the dairy coop.
When Rudy makes Timmy and Sam Kuramato believe they have killed Flip with a rock that Rudy actually threw, Timmy and Sam run away thinking that they are murderers.