Officer Michael Dooley prefers working alone, but, his boss assigns him a partner. The assigned companion is Jerry Lee, a German Shepherd detection police dog in the canine unit.
San Diego Police Detective Michael Dooley leaves his car to contact his girlfriend, Tracy, when a helicopter suddenly appears and opens fire on his car, which ignites. Presuming him dead, the assassins leave the scene. At the police station, Dooley argues with his lieutenant, refusing to take a partner; instead, he decides to get a police dog. At home, he finds Tracy with another man and spends the night in his new car. The next day, Dooley coerces Freddie, an informant, into revealing that the drug lord Ken Lyman is responsible for the attack. Dooley is assigned a German Shepherd named Jerry Lee,<ref name="LATimes"/> whom he dislikes.
Det. Dooley and his German Shepherd dog companion Jerry Lee set out to find a murderous man who plans to kill Dooley. During the movie, Jerry Lee becomes tired, and begins to fail doing his normal way of life. They also reluctantly team up with Sergeant Wendy Welles and her Doberman Pinscher, Zeus, who, according to Welles, was trained in the Netherlands and listen to commands in Dutch (although in reality the commands are in German). Eventually, they discover the attempter: a psychotic man named Devon Lane who thought Dooley's wife, Tracy, loved him more than she did her own husband just because she said that he "had talent". He also believes that Dooley was responsible for Tracy's death. Devon attempts to kill Dooley in a climatic showdown and, just in time, Jerry Lee jumps, tackles Devon, and takes him out. Devon is then arrested and Dooley is taken to the hospital for gunshot wounds. The film ends with Jerry Lee and Dooley creating their own exercise video.
After retiring, Detective Dooley and Jerry Lee have a retirement party with all of their friends. After the party, Dooley and Jerry Lee are both drunk. They enter LA Micro Labs and find a dead security guard apparently shot by criminals who have stolen a chip. Jerry Lee and Dooley must now track down the criminals and retrieve the chip.