The movie follows the adventures of Chance (a fun-loving American bulldog), Shadow (an aging, wise golden retriever), and Sassy (a snobbish Himalayan cat) as they accidentally get separated from their owners who are vacationing in Canada. After realizing that they are lost, the trio sets out to find their way back home across the Golden Gate Bridge to San Francisco.
Their journey is filled with many challenging obstacles, including dodging a gang of aggressive street dogs, getting trapped in a fire, and being chased by a fierce mountain lion. Along the way, they also meet new animal friends such as a sassy French poodle named Delilah and an old wise hermit cat named Rile who helps them navigate through the city.
Meanwhile, the family back home becomes increasingly worried about their missing pets and sets out on their own search party. They enlist the help of a concerned animal control officer who becomes invested in the search for the lost animals.
As the pets get closer to home, they must face their biggest challenge yet, crossing the dangerous Golden Gate Bridge. The film's heartwarming conclusion sees the pets finally reunited with their owners, much to their relief and joy. The film touches on themes of loyalty, friendship, and perseverance in the face of adversity.