Lassie grieves mightily when a raccoon she has befriended as a companion while Timmy returns to school after summer is killed by a careless speeding teen driver.
Timmy raises for a 4H competition a sheep that he is given by a truck driver for helping the driver retrieve a flock and then has trouble persuading a sheepherder that the sheep is his when it mixes with the man's flock.
A colt Timmy finds after a forest fire and wants to keep must be auctioned by the county and, when it appears Timmy will lose the bid, Washburne puts up money on the condition Timmy will house but then the mare comes looking for the colt.
Disobedient Timmy hikes in the woods alone because his hiking partner is sick and is knocked unconscious after slipping down an embankment as a forest fire starts.
Timmy and Paul's nephew Richard find a trapped falcon which Richard, a cadet and falconer, instructs Timmy to train and, when it is learned that Timmy is too young to keep a falcon, the falcon is donated to the Air Force Academy.
After Mr. Grisby, a railroad worker and friend of Timmy, is injured, Timmy offers to take care of Mr.Grisby's pet chimpanzee Casey while he recuperates.
Lassie is locked into transport trailer while Paul is selling the farm crop at market in Capitol City and, when the truckers open the trailer over 600 miles away, panicked Lassie flees into nearby woods.
While Paul and Timmy search for Lassie, Lassie still lost continues her journey escaping several dangers and is taken in by an hunter who treats her wolf bites and feeds her from his larder.
Timmy grows increasingly despondent at Lassie's absence so that he is unable to accept Cully's puppy while Lassie instinctively forges ahead toward home and arrives just as Timmy has lost all hope.
When Cully and Timmy attend the Capital City Dog show, they are given free perks and accommodations because Lassie is mistaken for an expected to attend champion dog but the promoter is not peeved as Lassie has often saved embarrassment.
Paul attempts to solve the problem of a beaver dam blocking area irrigation by trapping the beavers for relocation but Lassie's fondness for beaver causes Lassie to spring the traps while Paul dissuades a neighbor from shooting the beavers.
When the assessor loses his entry book prior to arriving at Cully's, he threatens to alert the citizens that Cully's bloodhound has no sense of smell unless Cully finds the book which is found in a bear cave by Lassie or the bloodhound.
Timmy obtains an unwanted German Shepherd to give to Miss Hazlit's uncle, a disabled in the line of duty police dog trainer, and then finds that the dog's deafness prevents training but Doc Porter does a corrective operation gratis.
Timmy trains a mixed breed of dogs for a junior sled race entered with some resistance from Paul and Ruth and then makes the mistake putting in the lead a hunting dog which goes off course when distracted by a rabbit.
After a pensioner Timmy has befriended is hit by a car when getting his check in town, Lassie brings his little dog from the man's cabin deep in the woods to the hospital in an attempt to revive the pensioner from a coma.
Timmy's and Cully's efforts to impress upon a forestry official the need to declare a certain section of forest a wildlife refuge in order to prevent the construction of the road backfire with sometimes hilarious outcomes.
Timmy and Lassie save a premature calf of a heifer Timmy is tending while the surly owner Mr. Tate is away and, when Tate wants to send the calf to slaughter, Timmy persuades an attorney to sue for possession of the calf.
Cully's treasure hunting friend foist on him a small elephant which Cully is unable to contain and prevent from damaging the Martin farm and other property in the vicinity.
An animal trainer permits his tiger to swim in the fishing hole at which time it flees at Lassie' s bark and terrorizes the Martins while Sheriff Miller's posse is on the hunt and the trainer attempts to prevent the animal's destruction.
Lassie secrets home and befriends a pigeon in a cage belonging to a magician who Lassie believes is harming the pigeon because Lassie does not understand illusion.
Timmy and Lassie adopt two orphaned foxes after the mother fox is killed by a hunter dogs. But Timmy must face the realization that now that they are able to fend for themselves they must be freed in order for them to survive in the wilderness.
Timmy convinces his friend Andy that he would take care of his pregnant dog Sibyl while he goes to the city. But when Timmy and Sibyl are going to Timmy's home, a speeding car hit the dog who runs away injured and hide out in a abandoned unsafe mine which lead to Lassie rescue.
The wild animals nesting in Cully's barn moved by Cully and Timmy temporarily to an outlying shed pending demolition of the barn by the county continue to return to the barn so Timmy writes a letter to the newspaper to save the animals.
When Paul and Timmy arrive to pick up some goats Paul has bought, a goat is found dead from anthrax so Timmy, Paul, Weaver and Simms must struggle to keep the remaining goats in the rocky cliffs to prevent a valley quarantine.
Lassie and Timmy endeavor to accustom Chief Washburne's dog Smokey to fire department noises and commotion so Smokey might overcome his fears and become an authentic firehouse dog.
A boy who is part of a marginal father and son clown and novelty animal circus act persuades Timmy to leave home and join the circus as a partner in an act which will feature Lassie.
Lassie assists a champion Irish Setter that craves relief from the strict regimen of the show ring stowaway in the Martins pickup to the farm and the dog's owner is displeased with the dog's behavior and treatment at the farm.