A mother cat is hit by a car so Lassie brings to the Miller farm the cat's new litter that Gramps wants to drown which is an action to which Jeff objects.
Jeff and Porky think they see a monster while fishing, and, while Gramps goes to the lake to see with the boys, Ellen sees it go into the house where, Gramps upon entering, finds a seal which the Millers keep for awhile.
Eccentric Sarah Dibbles, whom Jeff and Porky believe is a witch due to her stereotypical witch trappings, threatens a curse using the belief so the boys will discontinue spying on her.
Jeff's discovery of a wounded Mallard leads Jeff and Porky to the lake where they uncover market hunters violating game laws on posted land but when Jeff reports the infractions he is not believed because of the hunters' cover up.
When Porky finds his uncle's old mimeograph, Jeff and Porky decide to print a newspaper and, while looking for news stories, uncover a plot to swindle the town of Calverton.
A man who collapses by the Miller barn is found to be a clown on whom the circus owner has fled with the circus money so Jeff and Porky plan a circus at the church carnival but Jeff must prove first the man is not a thief.
While Ellen prepares for Gramps' surprise birthday party, Jeff's and Porky's attempts to help ease his day continually go awry and irritate Gramps who does not remember it's his birthday.
When the Millers receive Matt Brockway's brother's used television for Matt, Gramps' old-fashioned attitudes emerge but he watches the set anyway with Lassie who reacting to a program breaks the set for which finding repair is difficult.
When Lassie is impounded in Capitol City for lack of tag and leash, Jeff learns that most of the dogs in the pound are to be killed so he brings, much to the consternation of Ellen, the dogs to the farm so he can find them homes.
After Pokey disrupts Gramps' and Matt Brockway's checker game, Brockway gives Porky an ultimatum to train Pokey or else Pokey will be given away and the training does not go well.
After Jeff bests another boy in a fight, the other youth decides to exact revenge by claiming that Lassie bit him while his attorney argues that the dog should be killed for being a vicious nuisance.
The boy the Millers receive in a 4H youth exchange program is unexpectedly Japanese which stirs post WWII prejudices for some in the area to the extent the Miller farm is threatened.
During a storm Porky allows a raft the boys have built to drift into the lake so the boys must try to swim the lake during which Porky develops a cramp that endangers his life and requires rescue and help from Jeff and family.
Jeff's practice at being a vet results in the Miller cow not giving milk which he and Porky try to correct with ever worsening outcomes while the adult Millers and Brockways are away at a school board meeting.
The Millers mistakenly take a show collie home from the county fair instead of Lassie and legal charges are exchanged between the couple watching the show collie for owners in Europe and the Millers.
Jeff agrees to babysit a little girl at a time he was to join Porky in receiving rides on a road machine and so has Gramps temporarily relieve him without making sure that Gramps and the little girl understand the change of plans.
Traumatized over a bad accident in which a friend's mother was hurt, Jeff overreacts by trying to keep everyone safe even to the extent of keeping Lassie constantly on a leash.
Jeff is more motivated by competition with a dismissive schoolmate than by charity when the Sunday School class starts a collection for flood victims within their state.
An impoverished and dispossessed man whose son is a friend of Jeff's illegally hunts deer which he sells in order to obtain an operation to fix the boy's leg.
An unscrupulous horse tamer steals a quarter horse that Jeff has been slowly training to ride after the tamer cannot trick the Millers into giving him the colt.
A dog killing livestock in the area surrounding the Miller farm is discovered to be a son of Lassie who has turned killer as a result of abuse by a hired man of the former owners.
Porky and Jeff win a calf in a 4H calf scramble to raise and enter at the county fair to sell in order to buy an outboard motor but have second thought after the sale when they learn the heifer is to be slaughtered.
Stubborn, traditionalistic Gramps falsely blames the poisoning of Laddie on Matt Brockway's crop duster on whom he has called a Grange meeting to prevent further dusting in the area.
Jeff must prove that a former military dog who has unexplainably attacked the man who Jeff arranged to have the dog is not vicious but responding to some stimulus from army canine training.
When Jeff and Gramps are finessed by Ellen into going to Gramp's cousin's daughter's wedding, they hatch multiple plots to avoid the haircuts that Ellen wants them to have for the wedding.
When Jeff and Porky discover their competition jumping frog is female and about to lay eggs, they drive Gramps and Ellen to exhaustion in their quest to see the eggs are fertilized and produce offspring.
