Lassie and Corey visit Casey Howell who takes care of animals no longer able to survive in the wild. A tame mynah bird flies away and the collie feels responsible. Lassie worries about a hawk and heads into a rocky canyon to find the bird.
Lassie and Corey work on a soil erosion project to restore a watershed destroyed by fire. Corey brings a collie pup for a young girl's birthday .Then the storm arrives and sweeps the pup away giving Lassie a chance to save her..
While reliving some childhood memories of trips with his father, Corey is attacked by an escaped convict. Lassie and Corey follow the convict into an old mine which collapses and they all must find a way out.
Boone Sawyer has a unique ability to communicate with nature while protecting the animals. When hunters swear out an assault complaint against Boone, Lassie visits with him while Corey searches for a solution to his problem.
Corey, Dave, and Lassie are flying over a desolate canyon when their plane is struck by lightning. Forced to parachute Corey is injured and the collie is dumped into a raging river. Separated from the rescue area Lassie is left behind.
While Corey recuperates in the hospital, Lassie journeys homeward. A prospector confines her in his barn with his mule who helps her escape. Next the collie hops a freight train and joins two runaway boys, one of whom becomes quite ill. .
When Lassie finds a migrating goose that has fallen from the sky, she brings Corey to help the goose, whose devoted mate has also stayed. Lassie and the rangers race against time to get the bird an injection to fight metallic poisoning.
Lassie's friend Binks accidentally gets trapped in a refrigeration truck on a hot day when the driver leaves the door ajar. Lassie follows the truck back to its home base in order to get Binks released and returned home.
Lassie finds a mischievous chimpanzee named Debbie and takes her to the ranger station where she ruins the newly-cleaned station and creates havoc outside. Lassie gets some help from a raven before the big inspection.
Dusty, a lead pack mule, is being retired but he doesn't want retirement. Instead, he breaks away and follows his pack team with Lassie close behind him. His persistence convinces his human to let him continue packing.
Nancy is a physical therapist who uses tree planting to help her patients, four children who are disabled. Corey and Lassie arrive to assist her with the kids who respond eagerly. Jimmy is the exception who is depressed about his limitations.
Ranger Corey and Lassie take a troop of boy scouts for a camping trip during which Lassie finds a young boy following them. Andre, a young Frenchman, is following the scouts to learn from them as he knows nothing about woodcraft.
While playing and chasing a rabbit in San Carlos Canyon, Lassie and her old friend Spike are caught in a flash flood and trapped in the river as the waters rise. Rangers Corey and Barney work in tandem to rescue their beloved canines.
While in the desert visiting an old friend, Lassie and Corey meet an injured seagull. When he escapes his cage, Lassie protects him from several predators before he can accompany Lassie and Corey back to the ocean when they return home.
A serious reduction in trout has caused Andy McGrew's business to fall into disrepair. Lassie, Corey and a man from the fish and game department discover the cause of the problem with the trout and help Andy save his business.
During heavy rains and flooding, a group of logs break free and float down river. Lassie and Ranger Corey battle the rapids to string a chain line across the river to constrain the logs and save a bridge construction project.
In the Bristlecone National Forest where the bristlecone trees are ancient, the earth is fragile, and no off-road vehicles are allowed, two cyclists threaten the safety of the environment as well as the safety of Lassie's new friends.
After an outbreak of rabies is confirmed in one of their campsites, Lassie and Ranger Corey Stuart search for a boy who may have been bitten by a rabid squirrel and must be stopped for medical attention before he can leave the area,
When land is being cleared and burned to create new grazing land for cattle, Lassie plays protector to a family of rabbits caught in the upheaval. She helps them relocate and protects them from predators during their move.
Corey and Lassie visit a ranger whose wife is having trouble adjusting to her new life in the forest. When a ranger at Red Oak Station is attacked by a wounded bear, the wife and Lassie must assist the ranger and deal with the bear.
After a car accident injures a pregnant collie and her master, the collie tries to seek help for them. While Corey offers medical assistance to the young man, Lassie finds shelter for Lady and stays with her while she delivers her pups.