In this family comedy life is anything but ruff for Rex, Hollywood's hottest canine action hero. But this top dog is about to hit rock bottom when an aerial movie stunt goes wrong and the pompous pooch finds himself lost and alone in an unfamiliar city. Adopted by a rebellious 12-year-old boy (Josh Hutcherson), whose troubled dad (Bruce Greenwood) commands the ragtag crew of a rundown fire station, Rex soon learns the true meaning of loyalty and friendship while performing the most heroic act of all - bringing a father and son closer together.