When Timmy tears his new suit; afraid of being sent away, he blames Lassie so Ellen makes him choose a punishment for Lassie in hopes that empathy for Lassie will spur him to honesty but Jeff is skeptical and resentful of the plan.
After a circus train wreck, Timmy and Lassie find a baby elephant in the woods and Jeff and Porky want to use the baby in the back yard circus that they are holding to make money for circus tickets but mama elephant comes for the baby.
Jeff's and Porky's selfish promotion of the Spartan way of extreme self reliance to Timmy so a fishing outing can continue causes Timmy to avoid telling Ellen he is ill and results in Timmy contracting pneumonia.
When Gramps, Jeff, Porky and Timmy go to the Capitol City Zoo to visit the chimp once delivered to the Miller farm, the chimp stows away in the Miller car and is hidden on the farm by Timmy who fears imprisonment for theft.
Timmy has bad dreams after Lassie pulls his loose tooth by a string fastened to her collar but loses it hurrying to be with the family to watch a solar eclipse as Timmy is fearful of losing tooth fairy money and uneasy about the eclipse.
Timmy borrows Mike's bike to practice which he hides in bushes when sees Paul's truck and, since the bike is stolen, Paul tells Timmy to give Mike the new bike he has bought for Timmy so Timmy might finally get to school on time.
After Roy cancels a planned day with Timmy because he forced to go to the birthday party of a girl cousin, Timmy and Lassie begrudgingly acquire a play date with the unlikely companions of a girl and her pet goose.
Mrs. Grimes is asked to babysit Timmy and Scott while the Martins go to Capitol City but Timmy scams Mrs. Grimes into not coming after which the boys make a huge mess which they must summon Mrs. Grimes to manage.
Returning from buying a calf with Timmy who is increasingly ailing from measles along, Paul runs out of gas so sends Lassie with a note for help but Lassie is attacked by a territorial dog and then shot by a fearful mechanic.
When the worms Lassie finds prove special at landing fish, Timmy and Scott decide to sell the worms and when a wealthy fisherman refuses the worms in favor of his tackle, the boys continue to raise the price at the man's frustration grows.
When Timmy's school is to administer polio inoculations to the schoolchildren, Timmy who is afraid feigns sickness, does not give Ruth the permission slip and hides after the slip is signed but changes his mind after a visit to Weaver.
Uncle Petrie contemplates leaving the farm when is tale telling is believed to have caused Timmy to lose sight of reality when Timmy reports seeing a large gypsy and small ponies in the woods which Timmy has actually seen.
During a large snowstorm the deer start foraging in fields of the farmers which lead to special hunting permits to be issued, that when Timmy try to find a way to discourage the deer without any killing.
After Timmy becomes a Cub Scout, Paul is invited to bring Timmy and Scott to help with a Boy Scout outing while Scott's impertinent and taunting cousins Ralph and Bert spurn their invitation but come unaffiliated and start a fire.