When Stuart's truck is blocked by a landslide, Lassie must deliver an injection to counteract mineral poisoning in an important banded Canadian Goose in time for it to be effective to a female employee on assignment at the station.

Lassie races for help after an earthquake traps Corey under a tree in the path of a rock slide. Unfortunately the motorist who finds Lassie confines and drugs her then sells her to a vet conducting animal experiments.

While accompanying smoke jumpers, Corey and his partner Lane are trapped in the path of a fire. Both rangers are badly burned and rushed to the hospital. Lassie tracks them but encounters ranger Bob Erickson, who takes over caring for her.

The Forest Service must decide Lassie's fate after they realize Corey's recovery will take months. Lassie escapes from Ranger Bob's trailer to go to the hospital just as Corey is transferred to another one. Lassie has a decision to make.

While Scot is taking a tour with a bush pilot of Scot's new assignment in the National Forest of Alaska, a man in distress is spotted and on landing he finds the man has been attacked by a companion delirious following a bear attack.

Scott and Lassie are introduced to Johnny's adopted brother Neeka. The rangers survey an island where they rescue a female eagle that has fallen into the lake. Meanwhile Lassie protects the baby eaglet from a lynx.

While Dean and Scott continue to survey the water areas, Neeka and Lassie go fishing. When Lassie breaks her leg in a trap. Neeka must take charge of the situation. Meanwhile a wolf stalks the injured Lassie.

While repairing a gas leak on their boat Dean is knocked unconscious, so Lassie swims for help. She finds Neeka and Scott who are finishing up a series of glacier studies. Then they must wait for the Coast Guard to complete the rescue.

The livestock of a ranch on which Scott is taking samples to see if more grazing can be allowed is menaced by a jaguar from which Lassie must defend the ranch hound during an attack.

After Scott and Paul chase off a puma that has chased a jaguar from the injured hound Jason, Lassie leads Scott joined by Billy to track down and kill the jaguar.

Scott and Lassie visit Bob Erickson, who's affliated with a California university oceanography division. Lassie helps free a pelican tangled in a net then the bird returns the favor when Scott and Diane are trapped taking underwater photos.

When Bob and Al give the horses salt water therapy, Lassie protects a lost kitten from the perils of hawks and sea water while preventing a horse broken free after a bee sting from straying afar.

Two brothers have raised a calf as their 4-H Project. Russ had made a pet of Butch and wants to keep him while Ken wants to sell him for beef to pay their college tuition. When Butch wanders away, Lassie assists with the situation.

While Bob advises a developer on a desert development. Lassie and the developer's dog are imperiled by blasting and demolition.

Bruno is a war dog undergoing rehabilitation. When blasting occurs nearby, he panics and escapes. His trainer Mike warns all parties that Bruno is dangerous, then sets out with Bob and Lassie to find Bruno before anyone else can.

Archers begin hunting Bruno after he stampedes a corral of horses and kills a calf. Lassie finds Bruno and tries to lead him home. Then Buck is thrown from his horse and Bruno has a decision to make: will he attack or not?

On a trip to the Oregon coast Lassie befriends a mallard and her ducklings while Bob surveys a potential campsite. Danger lurks nearby in the woods from an unusual source.

While Bob tries to protect dunes from erosion near a lake at a dune buggy track, the club's pregnant dog Lady looks for a place to deliver her pups but ends up having them in the midst of the raceway. Lassie must help her.

While Erickson is assessing the danger caused by timber washed away by a flood, he allows former ranger Peterson to take Lassie on his boat to survey crab cages where Peterson is knocked unconscious with a storm approaching.

Newly conscious Peterson due to rough seas, timber debris and his condition cannot prevent his boat from drifting toward cliffs but Erickson drops seaward from a helicopter to contact a rescue boat which saves Peterson and Lassie.

The success of a camp for Job Corps volunteers is threatened when a crow steals a congressman's son's watch and implicates one of the volunteers, a former delinquent trying to turn his life around. Lassie must reveal the truth.

Lassie befriends a free-spirited young woman who calls herself "Walden" in homage to her idol, Henry David Thoreau. Aftershocks from an offshore earthquake endanger both Lassie and Walden, especially when Walden takes refuge in a cave.

It's a typical day for Lassie and Scott with the collie being interested in nature and it's wild creatures. But an Asian tiger being transported escapes and it's up to Lassie with her friends to locate the big cat before it does harm.

Scott and Lassie visit Neeka who takes Lassie with him to help collect and identify plants for a school project. They meet Clay Bowers, whom Neeka asks for help with his project partially to draw the unhappy man out of his shell.

While surveying riding trails, Scott, Lassie and Neeka camp out in a hotel in a deserted town supposedly haunted by the spirits of a wolf and the man who killed him. Many sounds including a wolf howl upset both Neeka and Lassie.

When Neeka's dad comes to town, Neeka decides to drive his truck. Although he and Lassie escape harm, the truck isn't so lucky. It. crashes and leaks gas. The resulting explosion frightens the horses and Neeka's own horse is badly injured.

Lassie meets a pair of flying squirrels. When one becomes trapped in a can, the mate seeks Lassie's help. The trapped squirrel is chased by a hungry coyote and then rolls down a cliff with Lassie and its mate following closely behind.

Two moonshiner brothers move into the Clear Lake National Forest in order to make their product undisturbed by the law. When ranger Bob catches Woody buying suspicious supplies, Leroy decides to distract the ranger by setting a small fire.