Winter turns to spring. During Kate's first hunt after her return, two Eastern Pack wolves interfere, and the caribou stampede. Thanks to Kate bundling them out of the way, everyone survives, but a fight breaks out, so Humphrey and his pals jump in and calm everyone down. The pack goes hungry that night, and Kate's father Winston decides to meet with the leader of the Eastern pack, who are even more hungry. She overhears her father and Tony, the Eastern Pack leader, deciding that Kate and Tony's son Garth will marry and unite the packs, so that they can avoid bloodshed.
That night is the Moonlight Howl, a social event where the wolves, usually mates, sing together beneath the moon. Kate meets her betrothed, Garth. He isn't all she'd hoped, however, with a voice so terrible it literally makes birds fall out of the sky. She makes an excuse to leave, and the obviously jealous Humphrey starts teasing her. They're hit with tranquilizing arrows and fall asleep.
They wake up in cages in the back of a moving truck. Shortly afterward they're released into a new park, and encounter a golfing French-Canadian goose, Marcel, and his companion, a duck named Paddy. After a brief chase, the two explain to Kate and Humphrey that they have been brought to Jasper park to "repopulate". They promise to help the wolves get home.
While Lilly, back at home, offers to show Garth around and jokes with him, Humphrey and Kate ride in the back of a camper. Humphrey's bladder results in them getting left behind. The two travel on foot for a while, facing a muddy gorge and angry bears. Marcel and Paddy direct them to a train that will bring them past Jasper. That night, while Lilly helps Garth improve his voice, Kate and Humphrey sing while on the train.
Lilly and Garth are interrupted by the Eastern pack arriving. Tony announces to Garth that they are about to take the valley, and the packs face off. Kate admits that she's had fun with Humphrey, and Humphrey almost admits his feelings for her, when they arrive home. Kate steps in and agrees to continue with the wedding.
On the wedding day, Humphrey says goodbye to Kate - he's leaving Jasper. The ceremony starts, but Kate finds that she cannot continue it, and announces that she has fallen in love with an omega. Garth is all too thrilled to admit the same. Tony, however, is furious since it isn't their custom, and orders his pack to fight. The caribou stampede, and Kate and Humphrey (who has changed his mind) try to stop them. Kate is hit by a caribou and lays motionless, and it appears she has died, while everyone howls in grief. She wakes up, and the two packs decide they can make this work.
At the next Moonlight Howl, everyone sings, even Marcel and Paddy. Kate and Humphrey stand on the top of the highest peak, and they reprise the tune they'd sung on the train.
Claudette and Stinky confront the strangers, but once the strangers get moving, they realize Runt is missing. They quickly return home, and the adults (Humphrey, Kate, Lilly, Garth, Winston, Eve, and Tony) dash off in pursuit. They realize the Banff pack is probably setting an ambush, so Kate and Humphrey go on ahead while the others go for backup.
Meanwhile, Runt has been brought to the Banff pack's home. The leader, King, had been rejected by Winston long ago. His adult daughter, Princess, cares roughly for Runt. Lily realizes that the Banff plan is to lure the alphas away and split the camp. That night, while everyone is asleep, Claudette and Stinky sneak away and meet up with Humphrey, Kate, and Paddy and Marcel (who they'd just run into).
Runt is still being held by the enemy pack, but Princess is warming up to him. Humphrey, Kate, and their other two cubs meet a lost bear cub. They're understandably reluctant to help it, after their experiences before. They eventually accept, though, thinking of poor lost Runt. Humphrey stands on Garth's back, pretending to be a very large alpha. King is interested in recruiting him, so they keep him talking while Kate comes from behind and rescues Runt.
While they make their escape, the Banff pack notices them fleeing and gives chase. They run into the bear cub's mother, and she and the other bears help the western pack. They win the fight, but on the way home, Kate and Humphrey and the pups get lost. Runt climbs a tree to see the way, and the family rides a log to make it to the human road quickly. They come across the gas station where Humphrey and Kate had been shot at. The man who had shot at them notices the pups, looks at a picture of his family, and then exits his house and drives away, leaving the door open. The pups go inside to see the tree, and it turns out he has left three small bowls of food there. That night, curled up warm beneath the Christmas tree, Kate comments to Humphrey that once again, they're trying to get home. Looking at their sleeping pups, Humphrey says that they are home.