After a recent earthquake, Ranger Corey Stuart and Lassie survey the prairie for damage. Lassie comes to the rescue of a colony of frightened prairie dogs threatened by a tarantula and badger and caught in a flood caused by the quake.
When an oil well explodes in flames, a pet terrier is injured in the blast. Lassie rescues the dog and follows her to the hospital to donate the blood needed to save her life.
Corey and his partner Bert enlist a widowed sailplane pilot in a Forest Service project to learn about wind-shears; meanwhile, Lassie helps hunt a marauder that savaged a ranch's chickens.
Lassie becomes the protector for a cougar, mistakenly shot as the ranch's maurauder, and her newborn cubs, while Corey accompanies Carol on her surveys.
Carol's unbroken mare escapes her corral and heads for the wilderness, oblivious to the danger from a maurading dog, while Carol must crash-land her glider.
Ranger Corey Stuart and Lassie travel to northern California to alert the community to the dangers of littering. The message hits home when a small fire is fueled by trash and oil-soaked rags, trapping a small dog in a dockside office.
Construction of a motel on Fawn Lake destroys the home of two ring-tailed cats. The homeless animals are separated and threatened by a stalking bobcat and Lassie must reunite them in a new home, far from encroaching civilization.
Beauty takes a back seat to progress as urban growth threatens the lakeside community of Fawn Lake. Ranger Stuart recommends an anti-pollution campaign, but warnings go unheeded until a photo of Lassie at the pristine resort serves as a wake-up call.
Ranger Corey Stuart and Lassie are stranded on a Glacier Peak when mechanical problems force their plane to land. In order to take off again, Lassie must be left on the ground, leaving her prey to a marauding bear.
Ranger Corey Stuart must use his plane to save Lassie from the attack of a marauding bear.
Lassie is paralyzed by a falling log and, rather than travel several hours by road to a vet, she and Ranger Corey Stuart brave a death-defying ride on a nine-mile wooden log flume to reach the vet in time.
A tugboat owner is temporarily blinded while in the Columbia River basin. Following the path of a log flume, Lassie leads the helpless man through dangerous territory and into the hands of friends.
Hunters are pursuing a family of deer when Lassie intervenes to help them cross a raging river. All the deer cross safely except a playful fawn, which is swept downstream. Lassie plunges in the torrent to save the young deer.
A man who professes to be protecting the forest tries to sabotage the Forest Service's new balloon logging program. After shooting at Corey's truck, cutting a telephone line, and sabotaging a bulldozer, he's ready to do even more damage.
A small girl's beloved dog is lost right before Christmas.
Lassie is out feeding her forest friends,when she comes upon a black lamb. The little creature was caught in a snare and being stalked by a coyote. Lassie chases away the coyote and chews the snare rope free. She is about to leave when the pathetically bleating lamb makes her realize it has no home. First she finds a flock of white sheep and the lamb runs up and eagerly nurses on a ewe. But the ewe doesn't recognize the black lamb as hers and savagely drives it away. Next they find a cow, and the lamb tries to nurse on her. But she kicks it away. By now the little fellow is so weak from hunger that Lassie wants to leave it while she reconnoiters, but a hawk appears, so first she must hide the lamb in some brush. To her relief, ahead she finds a flock of black sheep, but returns to find the hawk attacking the lamb, who has broken cover, and must fight the bird off. To Lassie's relief, the black sheep accept the black lamb. But a white lamb is loose in the flock of black ones, being reje
Corey escorts Miss Ridgeway, a nature painter of renown, to a secluded area where she can work, leaving Lassie with her for company. When her insulin supply is destroyed after a lightning strike sets her cabin afire while she is away painting, Lassie must help get her back to the ranger station over a treacherous bridge before she goes into a diabetic coma.
Corey, investigating a potential campsite at Emerald Forest, and Bill the resident ranger, are chagrined when well-meaning tourists rescue an ""abandoned"" fawn from the forest; believing the fawn's mother will not take it back, they plan to send it to a game ranch. But Lassie has other ideas.
Lassie rescues a coati-mundi's wayward kit--and a lost lamb as well--while Corey and his compatriots battles the forest fire threatening its home.
Lassie accompanies Ranger Corey Stuart on an avalanche control expedition. When the snow from a man-made avalanche buries a fox, Lassie must find the fox and dig her to the surface.
While Corey is at Cape Kennedy participating in a paracute-testing project, Lassie encounters Atlas, a guard dog gone wild after the death of his master.
Still in Florida, Corey and Lassie befriend Donnie Baker, whose puppy was run over while chasing a rabbit, and must rescue Atlas, trapped in the swamp.
Lassie has her hands full: she's reacclimating Atlas to society while keeping watch over a bald eagle injured during one of the parachute tests.
An animal trainer's truck crashes in the woods, freeing his animals in the wilderness. Ranger Corey Stuart tends to the trainer's injuries as Lassie retrieves the escaped animals, just as a vicious lynx is threatening to make a meal of Zelda, the pet raccoon.
A shutterbug Boy Scout is so intent on following an eagle to take a photo that he disregards where he is going and is trapped on a ledge.
Making a lake into a tourist attraction that will help a town depends on buying land from two independent boys the townspeople view as ""hippies.""
The Hanford boys refuse Corey's offer, to the outrage of speculator Wade, whose also worried because his teenager daughter Luci is attracted to ""the hippies.""
Wade faces off against the boys and is enraged when he finds out Luci has been helping them in their cause to keep their land from her father.