Zeus, a Labrador Retriever and a former police dog, has lost his bark after his barking ended up blowing off a five-year investigation and his partner can't shoot straight again and ends up at the dog pound. He is adopted by George Bannister as both an early Christmas present and as a good guard dog for the house, but the mom is hesitant and didn't want a dog. The dog is left home alone on Christmas Eve when the family head off to visit Grandma's house. A pair of burglars, Ted Stein and Stewey McMann break into the family home, and it is up to Zeus to save Christmas for his new family by setting up booby traps to stop them. Zeus soon gets caught by the burglars and they muzzle him and continue to rob the house. Zeus escapes while Ted and Stewey continue to rob the house. Zeus gets chased through the house by Ted and Stewey until Stewey accidentally pepper sprayed himself. Ted then takes out a tranquilizer gun and tries to shoot Zeus but gets Stewey instead knocking him out. Ted tries to escape the house (with Stewey who's still knocked out) but Zeus finishes them off for good by dropping a chandelier on them, knocking the two robbers out. The police come and arrest Ted and Stewey and Zeus finally barks. The family come back and see Ted and Stewey getting arrested and spend a Merry Christmas together.<ref name="her"></ref><ref name="blisstree"></ref>