The stock yard owner refuses Paul's lambs because the new foremen has his own suppliers but the foreman and his accomplice have an unusual source for the lambs using a goat which Lassie and Timmy uncover using a silent whistle.
Fearing army reprisal, Timmy and Don use Timmy's pet guinea pig as a replacement for one they let escape from an experimental space craft and in so doing expose themselves to possible radiation.
When a stray dog disturbs area farms, a conflict ensues between the farmers who wan to shoot the pest and the more human approach of Warden Smith with whom the Martins side. The dispute is complicated when the dog is trapped in a ravine.
Although not taken seriously at the grange meeting about a possible grasshopper plague, Timmy makes the Martins buy supplies to fight a grasshopper invasion and so the Martins are ready when an infestation is announced on the radio.
Timmy trades for a homing pigeon which he takes on Paul's business trip to test her ability to fly home. On the flight back it is attached and injured but rescued by Lassie with the help of a pigeon suitor.
After an Explorer lectures Timmy's Cub Scout den, the inspired den goes on a hike and wonder into the Badlands where they become stranded on a rock ledge.
Because hoof and mouth disease has been detected in the area so that the authorities want to destroy the Martin livestock, Timmy hides a cow that Paul has bought at a high price because the cow is about to calve.
Jed Ransom wants to shoot Doug Walker's minks blamed for killing area chickens until Walker shows Paul the footprint of a related but much more dangerous animal.
A developer's plans to flood Paul's alfalfa fields which Paul has rented for three years from a bank which gave Paul no notice of the title transfer result in unusual legal events as Timmy befriends the developer's daughter.
Timmy and his classmates buy a baby elephant to donate to the local zoo without acquiring the proper city authorizations so the Martin farm must house the animal for an unknown duration.
Timmy finds a badly hurt rooster that is actually a fighting cock which Ruth nurses back to health but one of the farmers who Paul supplies is an illegal cock fight promoter that steals it for a fight.
When Timmy joins a children's farm club pig raising competition, Timmy's piglet's growth lags while the piglet's continual escape from enclosure puts itself and Timmy in danger.
Chatty Mrs. Harper's belief that Timmy is frivolous with phone use causes her to leave her phone off the hook which makes it difficult to get help for Paul when a power line falls on his pickup during a storm.
To embarrass two hunters from the city for breaking farm fences Timmy and Cully create a false game trail but the trick goes awry when the terrain causes a shooting accident between the hunters.
A Martin lamb is attacked so Paul, Sam Burke and Sam's newly acquired German Sheppard which Lassie dislikes track a bobcat thought to be to blame and the Sheppard kills the bobcat with such ferocity that it looks like a trained killer.
The county is to build a new road taking six feet of farm land so Paul and Enders look for old stone monuments not moved during an original county survey to prove ownership while Timmy moves opossums to a fence to delay the county job.
An alligator escapes from a water circus and heads for a lake near the Martin farm where Flip and Timmy are put in danger time and again being unable to interpret Lassie's warnings and behavior.
Timmy's Mothers Day gift is switched with Willie's gift which is much more expensive but Ruth likes the gift so much Timmy is afraid to tell her and puts himself in danger to make good on a deal with Willie to pay her the difference.
Area folk dislike a hermit befriended by Timmy who is believed by Mr. Watson to have harmed Arnie but Arnie has slipped on to a cliff ledge and the hermit, a former climber, must rescue Arnie.
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.