Young Jeff Miller inherits a neighbor's collie and, while Lassie has trouble adapting to the Miller home, she is mistreated by the deceased's misanthropic hired man Wills who hangs on to steal the deceased's hidden cash.

Jeff considers running away when he is forced to study arithmetic including a special test after copying from Porky which study could cause him to miss the circus with Gramps.

Lassie leaves the farm when Jeff ignores her while he is infatuated with new colt Gramps has given him and after Jeff chastises Lassie for startling the colt.

Ellen, at first mortified by Jeff's discovery of his deceased father's rifle, allows him to play with unloaded weapon but Jeff proves reckless with the weapon when Mr., King loads it to kill a fox on his farm.

Jeff is enthralled by the plethora of tall tales told by the new farmhand Mr. Peabody but Gramps is chafed at folksy Peabody's partial falsehoods and peculiar ways and what he perceives as these things influences on Jeff.

Jeff is met at the lake by an escaped convict who threatens harm to Gramps and Ellen if Jeff does bring him clothes and food while being silent about the man's location.

Gramps get Jeff involves in a feud with Porky's father.

Jeff tells of seeing a lion in the woods but no one believes him until the lion show up at his home.

Jeff and Ellen wrongly believe that a Gramps has a bad heart and insist Gramps lie down for rest so Jeff trains Lassie to bark when ever Gramps assumes other than a prone position.

Lassie is in the barn and about to have puppies but looks ill at ease, and Tommy is worried. He wants to fetch a doctor but there is a windstorm which called Gramps away to repair lines. Without Gramps to help, Mom advises Tommy to pray. Later that night, the windstorm has died but Gramps is still gone, Tommy decides he just has to ride his bike 5 miles in the darkness to veterinarian Dr. Wilson but Mom won't let him. Tommy advocates for a world where kids can prevail with their perspective on doing the right thing. Nonetheless, he relents and is about to head for bed...

Ellen takes a job as singer at radio station in Capitol City and finds a small apartment that does not allow dogs so Lassie stays on the farm with Gramps but Ellen takes Jeff who is made miserable by lack of activities and a mean neighbor.

After Jeff' shows dog show operators Lassie's skills at a carnival, the two men steal the dog when Jeff will not sell her so Jeff jumps their truck to prevent the theft.

When Gramps has back problems, Jeff thinks Gramps will die if he does not have an operation the family can not afford and begins a twenty mile hike to Creston to sell Lassie to Porky's cousin to get the operation money.

Gramps and Ellen think that Lassie has developed a bad habit of chasing vehicles but Jeff's discovery about the selectivity of what Lassie chases uncovers an illegal cattle slaughtering operation.

A man who, unknown to the Millers, has been a prizefighter who killed a man in the ring signs on to be a Miller farmhand and is perceived by formerly admiring Jeff as coward for not standing up against another farmhand bully.

Ellen cares for a divorced old friend' s troubled daughter whose repressed anger is manifest in the destruction of things dear to others even to the extent that the girl will put Lassie mortal danger so Lassie will lose a racing contest.

When Lassie is to be quarantined because she is mistakenly thought rabid, Jeff and Lassie hop a freight train and meet a hobo who takes them home after some trouble in a hobo camp.

Ellen must go to a forgotten church meeting so she leaves a little boy for whom she is babysitting with Jeff and Porky, the two of whom suffer from the mean deeds and tricks of the boy.

Jeff whose father is deceased is told by a bully that he does not belong at the church father and son banquet but,, after Jeff rejects Gramps company, Ellen injects her self into the event and gains the participants' admiration.

When hunters kill a doe, Jeff rescues her fawn which Lassie is blamed for harming until livestock is killed by a canine believed to be a wolf.

After a couple whose son was blinded in the war and had a collie named Lassie try to buy Lassie for their son's adjustment, Jeff agrees to let the couple borrow Lassie for two weeks but Lassie's return goes awry.

Since Ben Nielsen is a liar, he is not believed when he tells that Jeff is trapped in a cave by a rock he has angrily moved in front of the cave entrance but can not budge.

Lassie sustains a severe injury after being hit by a car.

An unscrupulous water company executive trying to acquire by any means water rights from the Miller and other area farms is pushed into an old well by Lassie when he mistreats Jeff.

When Jeff is bitten by a rattlesnake, Gramps' truck axle breaks and he must try to carry Jeff to get a doctor and Lassie loses a note for help in a dog fight on the way to Porky's.

Jeff badgers Gramps to take him on a long promised camping trip despite Gramps' bad back and the two have good time with a fishing contest except when they are briefly accosted by an aggressive bear.