With the first snows of winter on the way, Zoe, Lassie and Harvey ignore Graham’s warnings and track a tagged bird they have released into the wild. The three rescue the bird, too weak to migrate south, but not until they’ve exposed themselves to a dangerous blizzard.

Zoe and Lassie take Harvey up a small creek to see a beaver dam and visit her family's favorite swimming hole. Realizing that the beavers - and the Creek itself - are threatened by a pair of unscrupulous gold miners who have snuck into the area, Zoe and Harvey take in on themselves to stop them.

When Lassie and the kids find an old treasure map in Mrs. Lee's store, it sends them on an adventure that reveals the truth about a notorious hermit who lived in the peaks of Grand Mountain. When Nick Connelly follows them, hoping to steal the 'treasure', he sets off a trap that endangers them all.

Zoe and Harvey witness a lightning strike that begins a forest fire. Making a heroic choice not to head for home, Zoe leads Lassie and Harvey up the mountain to a fire lookout, using the radio inside to alert her father to the fire. However, her eagerness to save a group of animals trapped by the advancing fire puts them all in danger.

Zoe, Lassie and Harvey are with Graham in a nearby town when Sarah calls them with an emergency. Mrs. Lee has been bitten by a poisonous spider and needs antivenin. Rushing home, Graham and the kids encounter a couple of tourists who have got themselves into trouble. Graham is duty-bound to remain behind. Now it's up to Lassie, Zoe and Harvey to find the quickest way into the valley... and that means rafting down the notoriously dangerous rapids.

It is rare that wolves will attack livestock, so when local Rancher angrily report that their cows are being killed by a vicious wolf, Sarah decides to head into the back-country to figure out what's really going on. With Zoe, Harvey and Lassie along, Sarah hikes into the high country to observe the wolves and see if the Ranchers' accusations could be true. When she discovers the real culprit, Sarah and the kids find themselves in a dangerous situation and only Lassie can save the day.

Skiing in a local resort, Zoe, Lassie and Harvey meet a reckless young teenager named Drew. The supremely confident older boy convinces the kids to try a run that Graham has recently closed because of the danger of avalanches. The run is steeper than Drew can handle. His thirst for excitement puts him as well as Lassie and the kids in danger. But as the kids work their way into the back country to find Drew, they find themselves face to face with a hungry wolverine... right in the middle of an avalanche zone!

Zoe and Harvey must ignore an oncoming storm to help a group of amateur tornado chasers survive outside in the dangerous weather. Luckily, with Lassie to help them, the odds are on their side.

Hiking in the forest, Zoe stays behind to hang out with some older girls she admires and Lassie heads for home on her own. When Zoe arrives home later, she's concerned to discover that Lassie never came home. Now while the whole community searches for her, only Zoe knows the dog well enough to find her.

Following Mrs. Lee's indications to find a special flower which may cure Biff, Lassie and the kids look for the home and garden of an aging hermit named Frances. The old woman seems mean and inaccessible and when the kids unintentionally infuriate her, they look like they may be in trouble. Things change when Lassie gives the kids some insight into Frances' true nature and they realize they're perfectly situated to help the old woman find a way to happiness.

Robert Humphrey begins running steam-train tours in Grand Mountain which Lassie and Zoe see are scaring the park's small herd of buffalo. Graham tells Humphrey he must change the train's route. Humphrey ignores the warnings and sends the train down an old and damaged track. Now, not only are the buffalo in real danger, but every passenger on the train is at risk... and only Zoe and Lassie can prevent a disaster.

Lassie and the kids have found a family of Black-Footed Ferrets living in the park! These rare animals are endangered and the kids are excited to see their den protected. At the same time, Robert Humphrey has come up with a plan to attract tourists to the park by paying Nick Connelly to impersonate a legendary "Loch Ness" style monster. When Humphrey's plan is more successful than he expects he sets off a stampede of curious tourists that threaten the endangered animals.

Humphrey's niece, Samantha, brings a group of girls up from the city for her birthday party, she and Zoe don't get along. When Samantha's choice of skating ponds puts her whole group in danger, Zoe intercedes, saving Samantha and finding a true ally - which is a good thing, because it's going to take both of them together with Lassie to save Harvey's life.

Zoe, Lassie and Harvey head into the high country with Graham when the waters of Diamond Lake begin to mysteriously recede, threatening the animals who drink from the lake. Graham fears that some obstruction may have blocked the flow of water. When the rangers discover a logjam that has dammed the creek that feeds the lake, they set to work busting it up... never knowing that Graham has become trapped in an underground channel that will flood the moment the logjam is broken.

When Sarah airlifts a wolf and her pups to another park for their own safety, Zoe discovers that one pup has been inadvertently left behind. Promising the tiny wolf that she will return it to its mother, Zoe, Lassie and Harvey begin to hike the pup out of the backcountry. The little wolf turns out to be a handful... and when it escapes from the kids, Lassie must face a mountain lion to protect the kids as they try to retrieve the cub.

After Lassie spots a condor that's been hurt in the wing, Zoe and Harvey must transport the endangered bird to Sarah's clinic. Lassie realizes the Condor has left a chick in her nest and the kids realize they must save TWO generations of this endangered species. With fewer than 400 of these rare birds left alive, their mission is a vital one.

Harvey's father was a famous rock climber who died when Harvey was just a baby. When a Park event leaves Harvey feeling the loss of his father very strongly, he sneaks away from the Valley to make the dangerous climb to a remote lake that was his father's favorite spot in the world. Guessing where he's gone, Zoe, Lassie and Harvey's mother, Beth, hike after Harvey, hoping to catch him before he gets into real danger. In the end, Harvey's own gifts and Lassie help the boy reach the remote lake and share a moment with his father.

The Grand Mountain Adventure Challenge is an annual contest for kids. The Challenge tests kids' abilities in canoeing, hiking, rock climbing and orienteering - and this year it has a 10,000 dollar prize. The unprincipled coach of one team kidnaps Lassie in hopes of taking Zoe and Harvey out of the race, but he has underestimated the kids' friendship with the other competitors, who join in the search for Lassie. And he has also severely underestimated Lassie's own resourcefulness and ability to escape. Zoe, Harvey and Lassie return to the starting line just in time to begin the race.

When Zoe and Harvey make a bet who can get home first, they take different paths. While Harvey follows the paths as indicated on his map, Zoe attempts to blaze her own trail. But without Lassie along to guide her, Zoe will get herself hopelessly lost.

Zoe's father Graham grew up in the Valley. His grandparents were some of the area's first residents. While Zoe knows a lot about her family, one mystery remains: there is a tiny valley where her father used to go that he never talks about. In fact he's never revealed its location. Harvey figures out where the valley must be and he, Zoe and Lassie hike in to discover the truth about the spot.

Zoe and her mother nurse an injured Grizzly cub back to health and release it into the wild. However, when Zoe realizes she may have just handed the little bear over to a poacher, she, Lassie and Harvey head back into the forest to set a trap for the poacher and rescue the cub.

The Grand Mountain Adventure Challenge begins with Zoe and three other teams competing. From the beginning, things begin to go wrong for each of the teams. One by one, each of the other competitors gets into some kind of trouble and Zoe and Harvey have no choice but to put their own progress on hold while they save their friends. They discover that these mishaps were no accident and come to realize that one team is cheating...

Zoe, Harvey and Lassie take a dangerous trip into the forest to find Zoe's beloved Aunt Kim, who has crashed her plane in the high country. What Zoe doesn't know, is that Kim was carrying a cougar in a cage - and finding Kim means walking into danger.

Zoe and Harvey are finally old enough to accompany Graham on the annual roundup of the park's wild horses. Working alongside a group of cowboys, the kids and Lassie help Graham drive the wild horses back to the valley where they can be well taken care of, and eventually placed safely on ranches in the area. When one pregnant mare goes missing, Zoe and Lassie can't leave her behind¿especially with rustlers in the area.

Lassie and the Parker family's attempt to spend a quiet day together having a picnic like a normal family is interrupted by constant emergencies. The family never actually have their picnic, but they do realize they're happiest when they're doing what they do best..."saving the day!"

When Sarah must head into the field to investigate an illness that is affecting the park's deer, Zoe is left in charge of the one fawn that appears to be resistant to the disease. When the little deer escapes, Zoe feels responsible and sets out to find him, taking Lassie with her.