Lassie rescues a hawk tangled in a kite string; the hawk returns the favor when a snake threatens Lassie's friend, a coyote pup, Next Lassie saves the pup from nearby rapids before finally needing help herself and receiving it from two young men on a hiking trip,
Lassie travels with the two men who rescued her. Ron and Dale have bought a treasure map and search for a gold mine. Once they find the location they're in trouble: a fire is headed for an old shed which contains dynamite.
Ron and Dale return home to the Holden Ranch where Lassie is welcomed by Garth Holden and his foster sons. The ranch is a working ranch and a foster home for boys. Lassie helps a withdrawn little boy who never knew his parents.
Ron and Lassie go to town to get a gift for Garth. When an earthquake hits, Ron is knocked unconscious and Lassie escapes from the truck. While Lassie helps other animals inconvenienced by the quake,.Garth helps Ron search for Lassie.
When Ron and Lassie return home from a trip, they find that Mike has adopted a raccoon. The raccoon is jealous of Lassie. Soon Lassie and Rags are feuding, which endangers both of them when a fire breaks out on a house construction site.
Mike befriends Henry Newton, an elderly man who flies a plane at airshows under the name of "The Flying Grandpa." Henry's tales of his own bravery during his air stunts impress Mike but seem to be untrue when a bear charges Henry and Mike.
While checking range land's suitability for grazing cattle, Garth and Dale see a young white stallion challenge the older black leader for dominance. .When the white stallion wins and drives the injured black stallion away, Lassie tries to lead him to safety.
Back at the Holden Ranch Garth and Dale leave food and water for the black stallion and hope he will choose to live at the ranch. The stallion once more visits his herd then accepts his new reality and returns to the ranch.
Home from college, Ron and Dale go out on the annual stray roundup. They make a bet as to which of them will find the most cattle. Meanwhile Lassie helps a calf stuck in quicksand and then helps Ron when he's thrown from his horse.
Out with Lassie, Ron and Dale spend a couple of days camping at Pine Lake before returning to college. They meet a boy who may be a runaway; he builds a campsite in the woods and then steals one of the motorcycles they've rented.
Lassie and Garth go to Vandenberg Air Force Base where Garth will be best man for one of his foster sons. While Garth attends a Minuteman missile launch, Lassie befriends a snow goose who has laid her eggs in a missile launching area.
A snow goose has laid eggs in the prohibited missile range zone. Lassie enters the area and manages to save the mother bird and her goslings. Later on, Lassie, back in Offut, becomes the friend of Sparky, a diabetic poodle. The trouble is that the doggie unfortunately stows away on the "Looking Glass"...
The presence of Sparky, the stowaway poodle, aboard the Looking Glass,is discovered. But as he has not taken his insulin dose, he is bound to go into a diabetic coma. Fortunately, Cameron receives permission to land and Sparky is saved in extremis. Later, Lassie and Colonel Stone get to know Jimmy, a crippled boy who does not believe in God anymore because of his condition...
Jimmy Fredericks doesn't believe in God anymore, but when his father's aircraft is stricken with a power failure that may interfere with the lowering of the landing gear and cause the plane to crash, the boy must re-examine his faith.
Garth takes Jimmy Fredericks back to the ranch. There Jimmy meets Lucy Baker, deaf most of her life, and her pet wolf Mountie. Unfortunately while he's playing with Lassie, Mountie is shot by a shepherd who doesn't know he's a pet.
Lassie hides Mountie in a cave where Lucy and Jimmy find him. Lucy sends JImmy for help on her horse. Despite being thrown from the horse, Jimmy finds the shepherd who shot Mountie. Meanwhile Lassie returns to the Holden Ranch. .
When Mountie dies, Lucy cannot understand why and goes into a deep depression. To help Lucy deal with her loss Sue asks her to help out at the wild animal park. Eventually Lucy begins to take an interest in the animals. Lassie also helps.