While trying to persuade Porky to go home, Jeff resists pressure to tell the whereabouts of Porky who has left home after an unwarranted licking because Jeff has made a promise not to tell.
After Lassie is professionally groomed for a family photo that Ellen won through a radio program, Lassie resists messy tasks and the surrender of her adornments.
When each of the boys boasts that the shooting ability of his father will win the turkey shoot, Jeff says Gramps, once a crack shot, will enter and win but Gramps has aged since he put the gun away ten years ago and comes a little short.
Jimmy Travis whose father is continually relocated gets his first dog but must shortly leave it behind so he has Jeff promise to care for the dog but the dog mourns and shuns food while waiting for Jimmy's return at the train station.
Jeff and Porky order two hamsters but receive by a mistake due to its misbehavior a chimpanzee from the same shipment which chimp must be kept over the weekend until it can be retrieved and it saves Gramps from a fall from the barn roof.
While the gang is at a wedding, Lassie runs after a bakery truck to a delivery, is taken on a hitchhike by transient worker at a delivery, given by the worker to a little girl from whom she flees and helped by campers before coming home.
Jeff and Porky fight because Jeff is more interested in the geode Lassie has found than finding Porky's lost new baseball and Jeff thinks Porky has said he is not interested in the geode that was to be entered in a class exhibit together.
A reclusive woman with a mongrel dog who rents an area home for the summer takes a dislike to the boys and Lassie so the boys make a trade of gifts between the woman and Gramps unknown to them attempting to change the woman's attitude.
Jeff and Porky while on a camping trip to practice survival skills are endangered by a forest fire started by a hunter who has carelessly managed a campfire.
On a bird watching assignment, Jeff an Porky witness a sitting Mallard duck killed by a ferret and, unable to find a brooding hen, have Lassie sit on the eggs until they hatch which causes the ducklings to adopt Lassie as their mother.
Gramps insists that Lassie stay outside in a dog house to catch a fox that is raiding the hen house but Lassie does not feel welcome back inside after she kills the fox.
While having a bad day, Gramps leaves the farm thinking Lassie is more valued than he but later needs Lassie's help when pinned against his pickup by a tree that falls during a storm.
Ellen's and Gramps' talk diminishes Jeff's passion that Jeff and Porky will be Calverton constable and deputy constable on boys' day so Gramps arranges a fake bank robbery with his friends.
Jeff is embarrassed by his humble circumstances when the son of a wealthy banker and family take residence nearby while the rich boy is envious of Jeff's country lifestyle.
When Jeff accepts a dare to enter a rumored haunted house, Jeff and Porky become trapped in a cellar by the actions of a secret society initiation, the members of which the boys believe to be ghost because of their colonial dress.
Jeff and Porky vow to protect a pair of band-tailed pigeons rare to the area that have nested in the farm mower but Gramps might have to disrupt the pair to cut the alfalfa in advance of a fast approaching hail storm.
When fatherless Jeff shuns the 4H meetings because each father is in turn teaching a task, Ellen attempts to engage with Jeff in physical fatherly activities thinking Jeff is lonely but this behavior causes Jeff to think the same of Ellen.
When a peddler relates to Jeff and Porky a lie told to him by Gramps about going broke, Jeff starts taking drastic action such giving Lassie to Porky to feed, selling his things and readying to leave school to get a job.
Lassie finds a wild Gravenstein apple tree that Jeff and Gramps can use to graft the trees in the orchard after rabbits have girdled them so the orchard and farm can be saved.
While Jeff helps the boy with his education and Gramps tries to arrange a lease for the father, belligerent Jud Perkins wants the 'foreigner' squatters on an area farm removed by any means necessary.
Jeff's belief that he is growing facial hair, not obvious to anyone else, causes him to aspire to manhood but he both finds it difficult to forgo some of the pleasures of childhood and to accept adult duties per Gramps accounting.
When Timmy tears his new suit; afraid of being sent away, he blames Lassie so Ellen makes him choose a punishment for Lassie in hopes that empathy for Lassie will spur him to honesty but Jeff is skeptical and resentful of the plan.
Jeff who is working for Dr. Weaver leaves Timmy in charge for a few minutes to assure the purchase of a discounted baseball glove and Timmy frees a biting dog under observation for rabies.
While Ellen and Jeff go to a dinner, Timmy and Gramps go on a berry picking trip on which Timmy eats poison berries but fortunately Timmy has called the doctor because he thinks napping Gramps is ill.
After a circus train wreck, Timmy and Lassie find a baby elephant in the woods and Jeff and Porky want to use the baby in the back yard circus that they are holding to make money for circus tickets but mama elephant comes for the baby.
Jeff's and Porky's selfish promotion of the Spartan way of extreme self reliance to Timmy so a fishing outing can continue causes Timmy to avoid telling Ellen he is ill and results in Timmy contracting pneumonia.
When Gramps, Jeff, Porky and Timmy go to the Capitol City Zoo to visit the chimp once delivered to the Miller farm, the chimp stows away in the Miller car and is hidden on the farm by Timmy who fears imprisonment for theft.
Thinking it is a dog, Timmy brings a wolf pup to the farm which draws the mother to the house and opens discussion about the pup's destruction which Timmy has trouble accepting.
Timmy has bad dreams after Lassie pulls his loose tooth by a string fastened to her collar but loses it hurrying to be with the family to watch a solar eclipse as Timmy is fearful of losing tooth fairy money and uneasy about the eclipse.
With Gramps death, Jeff and Ellen are faced with moving to Capitol City and Timmy with going with his aunt and uncle but the Martins agree to take over the farm and adopt Timmy.
Timmy has trouble accepting Ruth as his mother and Ruth compounds the problem by wanting Lassie kept out of house to the extent that Timmy attempts to send Lassie to Jeff and Ellen Miller.
Timmy borrows Mike's bike to practice which he hides in bushes when sees Paul's truck and, since the bike is stolen, Paul tells Timmy to give Mike the new bike he has bought for Timmy so Timmy might finally get to school on time.
After Roy cancels a planned day with Timmy because he forced to go to the birthday party of a girl cousin, Timmy and Lassie begrudgingly acquire a play date with the unlikely companions of a girl and her pet goose.
Mrs. Grimes is asked to babysit Timmy and Scott while the Martins go to Capitol City but Timmy scams Mrs. Grimes into not coming after which the boys make a huge mess which they must summon Mrs. Grimes to manage.