On her way home from shopping in Capital City, Ruth skids on the dangerous muddy cliff road and is left teetering in their pickup truck on the edge of a cliff. Lassie to the rescue.
When Timmy friend Ricky returns to France he gives his dog to Timmy, Timmy however gives the dog to Cully after the death of Cully's dog. But the new dog causes Cully problems and Timmy begins to regret his decision.
As a result of Washburne showing a fire prevention film at the school, Timmy removes fire hazards from Charlie James' barn creating an unintended disturbance which causes James to petition the city to remove Washburne as chief .
When Timmy and Cully visit a abandoned cabin of a deceased man who supposedly had a hidden treasure hidden away they come across an eagle inside clutching a pouch which Timmy believes to be the hidden treasure.
Cully leg is trapped by a boulder after being caught in a landslide when he and Timmy were trying to get to the eagle's nest to get a pouch which they believe to be missing hidden treasure.
While looking for butterflies for a nature school project in the Martin peach orchard Timmy and Lassie discover the orchard has been infested by the destructive gypsy moth.
When Timmy enters a Camera Club contest Timmy attach a camera to a kite to get a aerial photo, but kite and camera get caught on a high tension power wire over a neighbor stable which catches fire from the sparks.
During a time when Timmy has organized a wild animal feeding program in a severe winter for which the local farmers blame a surge in wolves, a quaint toy repairman traveling with a donkey wagon lodges with the Martins at Christmas.
It is a bustling Christmas for Calverton as Timmy sings a solo at church and the Martins host a party while Lassie rescues the cubs of a wolf Krebbs has killed and Nicholson disappears with the cubs as mysteriously as he arrived.
Timmy is begrudgingly allowed by the Martins to raise an orphan colt that is born blind and with Lassie's help overcomes challenges he experiences in the process.
While hunting for quartz for school, Timmy sees Square Deal, a stallion he and Mr. Washburne once co-owned which Timmy set free. The stallion is stealing horses to form his own herd, but the owners of the stolen horses want to shoot him.
To help with the Martin's financial bind, Timmy hitches a ride to a distant town to enter canine field trials to win the prize money for which he must put up Lassie for the unexpectedly high entrance fee.
The Martins reluctantly leave camp and return home without Lassie. Meanwhile Lassie has been rescued by a forest ranger, Corey Stuart, who is staying at a friend's cabin on the lake. As Lassie recovers she and Corey form a bond.
Having mostly recovered now, Lassie accompanies Corey as they search for an inexperienced hunter who is shooting animals out of season and who has carelessly and inadvertently started a forest fire.
Lassie goes on avalanche patrol with Corey. When he and ranger Tom Baldwin leave the station to dynamite two final dangerous buildups of snow, Lassie becomes very uneasy. Meanwhile, Timmy learns that Lassie is still alive.
Lassie rescues Corey and Tom Baldwin, both of whom have been buried in an avalanche. Corey makes a sled to transport the injured Tom, and they begin their trek back to the ranger station .. Lassie and Timmy are reunited.
Sheep begin to disappear and reappear. Lassie and Timmy investigate and find that an old shepherd and his sheep dog have been borrowing sheep to practice their trade. The local farmers decide to employ the man and his dog and share them.
Timmy buys an expensive new CB radio and takes it up to Indian Cave to test it. On the way to the cave, Timmy and Lassie are caught in an earthquake and threatened by a crack in the Rock River Canyon dam. .
Lassie and Timmy find and rescue four piglets then go looking for the mother sow. They find her, a fifth piglet, and the bobcat whose attack caused them to be separated.
Duke, a guide dog for a blind attorney, is traumatized when a motorcyclist collides into him and his master. Lassie and Timmy work to rehabilitate Duke, but it's love and concern for his master that completes Duke's rehabilitation.
Paul rents a bee hive for bees to pollinate his peach crop. When a skunk knocks over the hive, Timmy finds a new source of bees, but poor Lassie gets sprayed by the skunk, thus ending Timmy's hopes for a blue ribbon at the dog show.
On his way to school Timmy is the victim of a hit and run when the driver swerves to miss Lassie and runs Timmy off the road. Lassie is the only eye witness to the accident and she takes a souvenir from the driver.
The return of Old Blaze, a marauding wolf-dog, does not please the local farmers; however, when a naturalist professor falls from a cliff, Old Blaze leads Lassie to the injured professor thus saving both the professor and himself.
Timmy and Lassie find an injured raccoon in the woods and nurse it. The raccoon repays them by raiding Paul's hybrid corn and bringing his friends. To keep Paul from shooting the animals, Lassie and Timmy spend the night in the corn patch.
