Ranger Steve John Rhys-Davies sits by a campfire, weaving a story about the Davis family for a listening crowd.
John Davis William Hurt is flying a water plane over a valley called Sasquatch Valley with his two daughters Khristy Jewel Restaneo and Maggie Blaire Restaneo. Khristy explains that a Sasquatch means Bigfoot, and Maggie wonders if there are any Bigfoot in the valley. Khristy insists that Bigfoot is a myth, even as they arrive at their new home, a place strewn with pine cones. By nightfall, the house is cleaned up and everyone heads to bed. In the shed outside, Maggie hears a noise and discovers a small bigfoot hiding there. She trips, and the little creature scampers away.
The next morning, John, Maggie, and Khristy head to John’s new job, where they meet Dave Joe Alaskey, the plant boss. A plan to build a new dam on a nearby river to provide power for the area is laid out, while Cletus McNabb Lance LeGault and his sidekick Dawg Brian Cummings quietly plot to catch a real bigfoot.
That night, Maggie again goes outside to search for the elusive creature. She finds him once more and chases the bigfoot far into the forest. It starts to rain, and the bigfoot returns with his mother, Momma Sasquatch June Foray, leading Maggie to a secret cave beneath a majestic waterfall. The bigfoot then takes Maggie back toward the valley, while the looming threat of flooding from the dam hangs over their home.
The next morning, Maggie tries to tell John and Khristy what happened, but they don’t believe her. Later, Ranger Steve’s visit confirms that John asked him to check in on the family, but Maggie remains worried and Khristy remains skeptical. Frustrated, Maggie bolts off to find the truth, with Khristy racing after her. The sisters eventually reach the secret cave, just as Cletus McNabb Lance LeGault and Dawg Brian Cummings spy them and devise a plan to trap one of the bigfoot.
John returns home and searches the forest for his daughters. When he finally finds a bigfoot, the two of them are guided to the cave, where John realizes the danger facing the creatures they’ve stumbled upon. A plan forms to save the cave from flooding. They stack and grind pine cones into a pulpy slurry, then haul it into the fissures in the cave, sealing cracks and buying the creatures time. The group wonders if the walls will hold, so they relocate the pine pulp to a higher, safer cavern high in the snowy mountains.
Cletus and Dawg push deeper into the flooded cave search, but the rocky tunnels begin to close in around them, and a surge of water forces them to retreat. Up in the mountains, the Davis family says goodbye to the remaining bigfoot, who have found safety away from the looming threat. In the final moments of the credits, Dawg vents his frustration with Cletus and decides to move in with the Davis family, sealing an uneasy, unlikely alliance.
