When Jerry Johnson who wears an unneeded leg brace visits the Martin farm with his Collie Blacktail, Timmy is asked to help Jerry overcome his dependency on the brace.
After observing Cully Wilson's special way with animals, Timmy befriends a wild skunk which causes Lassie, Ruth and Miss Hazlitt consternation and trepidation.
A helicopter pilot doing conservation seeding who Timmy has befriended rescues Timmy when Timmy slips from a cliff to an unstable ledge while he is chasing an escaped pregnant ewe.
While Ruth runs an errand, Mrs. Wilder brings her twins early due to a schedule change so Timmy gets a babysitting responsibility, a task complicated by a hawk which flies into Timmy's room chasing a pigeon and creates havoc.
During his work as a water boy for carnival animals about which Ruth is anxious and disapproving, Timmy carelessly allows an untamed tiger to escape his cage.
During a time when the animal is menaced by a wolf and a wounded rogue bear, Timmy aids an injured fawn which he tries to make a pet against Paul's advice.
Timmy asks Ruth to give neighbor boy Bob a job so Bob can pay Doctor Weaver for a cataract operation for his blind dog whose condition puts the dog in constant peril.
The Martins attempt to prevent the demolition of an old mission in Calverton because it appears a group of swallows have chosen to make it their recurring spring home.
When Timmy mistakes scuba diving Dave Tanner as a sea serpent, Tanner decides to perpetuate the idea to secret his discovery of fresh water pearls he has found in lake mussel shells but puts himself in danger.
The Walkers' colt that the Martins are stabling for the summer breaks a leg and is put in a sling by Dr. Hayden but Ruth wants the horse destroyed rather than be miserable and so does Mr. Walker when he unexpectedly returns.
The Martins care for a spoiled and mischievous poodle of an actress who has wrecked her car near the Martin farm so the actress can keep an appointment while her car is repaired.
Timmy's and Willie's building an entry for a go-cart race proves detrimental to Timmy's performing his duties for the farm but Timmy's mechanical construction is still shoddy.
A drought has brought down from the hills a bobcat trailing deer which threatens Timmy caught in a trap and Bob has carelessly shot Lassie with an arrow.
Timmy befriends two poor children staying in a tool shed with the father who is fleeing authorities to prevent the children's placement in foster care so the Martins acts of charity include getting the man a job to support the children.
Paul threatens to shoot a neighbor's champion bull, an often escapee from his quarters, after it almost kills Timmy and then is accused of the demise of the bull when it is actually poisoned by the neighbor's bitter hired man.
Timmy observes what he believes is a wild horse which becomes a menace to the local farms but persuades Paul to convince the local farmers to spare the life of the horse which is later learned to be an escaped thoroughbred.
In Paul's absence, Timmy is unable to shoot a dog strayed on to the Martin farm that has become rabid because he and Lassie have befriended the dog before the dog contracted disease.
Lassie is accidentally ejected from a train baggage car during a trip the Martins are taking to Chicago where Paul is to be the local representative to the national Grange committee.
A trained war mule that Cully has received for a WW1 veterans parade goes berserk after eating dried lead base paint dropped on hay and is threatened with destruction by authorities for being a dangerous animal.
When Timmy learns at a Nike base that the military needs German Shepherds, he rescues an abused dog from the pound to train for military use but the dog's dispirited nature proves an frustrating obstacle.
When Timmy sees a man destroy an eagle egg, Timmy replaces the egg with another egg, a goose egg. To Timmy's surprise the eagle accepts the gosling when the egg hatches.
An impoverished family fleeing a drought stricken farm stay overnight with Martins after Timmy draws them in by a prank but the family's boy runs off into woods during deer season when he hears his dog cannot be kept.
At Paul's offer to pay Cully to use Cully's farm, Cully sees it as criticism of his age and overworks himself to correct the perceived insult until Lassie works with Cully's old dog to show old and young can work for the benefit both.
Ruth acting as a volunteer fire watcher and Timmy are endangered in the watchtower when a carelessly discarded cigarette starts a forest fire and a ranger near the fire has been thrown by his horse frightened by a snake.
An operator of a carnival dog show dog-naps and disguises Lassie for Lassie's ability to learn trick when the health of his main canine performer falters .
A sea captain has brought a male ostrich for a fair sulky race but must prove to the judge that the bird is ready to race a horse and the captain must call on Timmy to drive while Ruth is reluctant due to a nesting female's aggression.
Timmy and Cully search for a gold mine after Lassie find a gold miner's burro which leads to problems for both of them and which Lassie comes to the rescue.
A girl's horse who is past his rodeo glory days is made skittish by an apprehension of Lassie and later that apprehension will prove useful in resurrecting the rodeo career of girl's father returning to the arena after injury.
Lassie finds a doll that could be a clue do the location of a missing six year old city girl at time when a huge aqueduct ditch is about to be filled by a significant amount of water.
Timmy erroneously believes that his operation of a machine he and his friends have made to contact Martians has caused an army plane to crash but the army believes that Lassie's behavior at the time of crash is a clue to accident.
