San Diego detective Mike Dooley sits in his car on lover’s lane awaiting an informant. Realizing he is going to be late for a date, he asks a partially dressed couple in a Rolls Royce to use their car telephone. A helicopter appears and a hoodlum, “Benny the Mule,” machine guns Dooley’s automobile before flying away. Dooley rushes to the police station to request another car. Lieutenant Roger Byers refuses to give him one unless he takes a partner. Dooley insults Byers, and Byers punches him in the face. Arriving home three hours late, Dooley finds a romantic dinner set out on the table. He apologizes to his girl friend, Tracy, who accuses him of putting work before their relationship. The next morning, Dooley spots his informant, Freddie, who failed to show up the night before. As payback, Dooley takes Freddie on a “jog” by handcuffing him to his automobile and driving down the street. Freddie confesses that Ken Lyman, a major drug dealer who pretends to be a businessman, is storing narcotics in a warehouse complex, but suggests that Dooley will never find the drugs unless he has a “great nose.” At a crime scene, Dooley persuades K-9 officer Brannigan to help him get a police dog. Brannigan takes him to the police kennels and warns him that the available dog, Jerry Lee, is semi-retired due to stress. Dooley suits up and enters the cage, but the dog does not react. Brannigan suggests Dooley give a command. Dooley yells “Kill!” Jerry Lee attacks, bringing Dooley to ground. Brannigan brags that Jerry Lee is the best drug-sniffing dog in the city. At the warehouse Freddie told him about, Dooley is humiliated when Jerry Lee does not follow his commands, until he tells the dog to “find the dope.” Just as Ken Lyman appears and asks Dooley for his search warrant, Jerry Lee runs up to a small shed and barks. Dooley replies that the dog smells drugs, therefore he does not need a warrant. He kicks the door down to find a worker smoking a marijuana cigarette. Lyman asks if he should call in a task force for one “joint.” Infuriated, Dooley drives to a dive bar and orders Jerry Lee to stay in the car. Inside, Dooley interrupts a barroom brawl in progress. Everyone stops when Benny the Mule identifies Dooley as a cop. When thugs leap on Dooley, Jerry Lee comes in snarling. Benny hurls a cue ball at the dog, who catches it, bites it in half, and attacks. Jerry Lee soon has the men against the wall. Benny picks up a pool cue, and Jerry Lee bites him in the crotch. Dooley urges Benny to talk. Benny blurts out that Lyman is making a drug deal with a man named Gilliam. Uniformed police arrive, and Benny is arrested for attempted murder. Dooley steps outside and berates Jerry Lee for losing his composure and leaving the car. Jerry Lee buries his face in his paws to show he is sorry. Claiming the dog stinks, Dooley buys Jerry Lee “doggy deodorant,” but the canine almost bites his hand off when he sprays it on him, so Dooley runs the dog through a car wash in a convertible with the top down. Dooley lectures Jerry Lee that he is boss and will always win an argument, and the animal responds by biting out the car radio. At Lyman’s mansion, Freddie promises he did not tell Dooley about the warehouse. Lyman shoots him in the head and orders his right-hand man, Dillon, to kill Dooley. Dooley takes Jerry Lee home, pretending he is a gift for Tracy. She instantly falls in love with the dog and instructs him to do tricks. When Dooley tries to kiss her, Jerry Lee snarls. Dooley takes Jerry Lee aside and informs him that Tracy is his. The next day, when Dooley goes to a fancy restaurant, he ties Jerry Lee to the car mirror so he will stay. Inside, he identifies Gilliam, Lyman’s partner, by having a waiter bring the criminal a bottle of champagne. Jerry Lee arrives, dragging the car mirror behind him as Gilliam leaves. They follow Gilliam to the beach, and observe him meeting with Lyman. However, before Dooley can get close, Jerry Lee spots a flying Frisbee and gives chase, dragging Dooley with him. Later, at a doughnut shop, a hitman takes a shot at Dooley and drives off. During the ensuing car chase, the hitman crashes into a woodshed, then flees on foot. Dooley and Jerry Lee pursue the man across rooftops until he slips and falls through a skylight. A quick search of the would-be killer’s car leads them to a Mercedes dealership. Halstead, the owner, says he recently reported a Mercedes was stolen from his lot. Jerry Lee smells drugs in a red convertible, but Dooley drags him away, explaining they will wait for Halstead to make the exchange with Lyman before making any arrests. Dooley returns home to discover Tracy has been kidnapped. A message on his answering machine promises that if he lets the drug shipment go through, Tracy will be released unharmed. Dooley drives to Lyman’s mansion, where he finds a dinner party in progress. He accuses Lyman of being a murderer and drug runner, and puts a gun to his head just as police arrive and drag him away. Lt. Byers puts Dooley and Jerry Lee under arrest. As Byers drives to the police station, Jerry Lee passes gas, causing Byers to pull over and let the dog out. When Jerry Lee does not return, Byers and Dooley step out to find him. Dooley sees the dog sneak back into the police car, leaps in, and drives off without Byers. Back at the dealership, Dooley watches Halstead get into a car carrier full off automobiles. He sounds the siren and orders Halstead to pull over. Instead, Halstead opens fire with a shotgun, blowing out Dooley’s engine. Jerry Lee leaps into the carrier and forces Halstead to stop. Dooley drives the carrier to the drug rendezvous. Spotting Tracy in Lyman’s car, he holds up what looks like a detonator and informs Lyman the car carrier is wired with explosives. The drug buyer arrives in a helicopter. Dooley offers to swap the carrier for Tracy, but as Lyman is ready to make the exchange, the device in Dooley’s hand beeps, revealing it to be a handheld video game. Bullets fly as Jerry Lee springs from the carrier and attacks Dillon. Lyman shoots Jerry Lee and races toward the helicopter, but Dooley kills Lyman, and the helicopter lifts off. Tracy and Dooley rush Jerry Lee to a human hospital, where a doctor refuses to operate on the dog. Dooley pulls his revolver, declaring that Jerry Lee is a cop and his partner, and the doctor changes his mind. Later, Dooley finds Jerry Lee unconscious and thinks he is dead. Jerry Lee wakes up, but keeps his eyes shut as Dooley apologizes for how badly he treated his partner. When he realizes Jerry Lee is faking, Dooley reprimands him, but calms down when the dog licks his face. Days later, Dooley takes Tracy and Jerry Lee on a vacation to Las Vegas, Nevada.