After being separated from her companions in a canyon plane crash, Lassie endures captivity, hops a freight train with runaway boys, battles a wolf, stops a stampede, saves a man, and overcomes injury—guided by a hawk—until she finally returns home.

When livestock falls prey to a wild dog, local farmhands mistakenly accuse a mother cougar and her cubs of hunting their heard. It's up to Lassie and her owner, Forest Ranger Corey Stuart, to identify the real culprit and keep the young cougar family out harm's way.

At Cape Kennedy the testing of parachutes for the lunar module injures an American bald eagle. The race begins to see which bird will launch first: the lunar capsule or the bald eagle.

After a storm strands Lassie in a lake during a camping trip, she is left behind by her owners until she is rescued by a forest ranger. During her recovery, Lassie bonds with her rescuer and eventually joins him to track down an inexperienced hunter whose reckless poaching has inadvertently sparked a forest fire.

During a hurricane in Florida, Lassie becomes trapped on a ship bound for Hawaii and ends up overboard. After being rescued by a dolphin and reaching Virginia, she is mistaken for a dangerous stray in Williamsburg, where an elderly lawyer and his assistant come to her defense.

Sally gets surgery for her hearing. Lassie gets lost after having to hide out in the back of a laundry van.

The Scottish collie Lassie goes to Alaska. There Lassie meets the Indian boy Neeka, who stays in the woods with his stepfather, who is a Ranger. When on behalf of his school Neeka is collecting plants for his herbarium both Neeka and Lassie have a lot of adventures.

The Holts and their friends search for the runaway Kerry but he is with Lassie and her pups. After a dangerous encounter with a mountain lion Kerry is found. Lassie leaves one of her offspring before continuing her journey.

The Stratton kids, Samantha and Chip, and their grandmother, Ada, drive to visit their Uncle Stuart. Grandma collapses and dies in a strange town, leaving the kids and Lassie on their own.

Young Timmy Martin's world falls apart when he learns that his family must move to Australia. Lassie is to remain in America, so the Martins search for a new home for the Collie. Neighbor Cully Wilson takes Lassie in, but the old man already has a dog, the cheeky Yorkshire Terrier named Silky. Lassie is now constantly occupied with keeping the small dog in check.