Nova Robotics in Damon, Washington, has developed a new line of laser weapon-equipped robots called Strategic Artificially Intelligent Nuclear Transport (SAINT), which have tank-like tracks for movement. At a cost of $11 million each, five robots have been built, each capable of being parachuted into enemy territory and transporting a nuclear bomb into position. SAINT inventor Newton Crosby envisioned the robots for non-military uses, but the military establishment sees them as the “ultimate soldier” that will follow orders without question. After the robots offer an impressive demonstration to military and government officials, a bolt of lightning hits the generator recharging robot Number Five. While Five initially seems to be fine, it quickly starts bumping into walls and malfunctioning. Five accidently gets onto a garbage truck leaving the Nova Laboratories compound, but then falls off, landing in a pasture. When Nova officials discover Five is missing, Newton Crosby contacts it, but Five signals back, “Malfunction. Need input.” Nova officials learn Five’s whereabouts with a tracking device and send a team to get it. They are worried because Five’s laser weapons are still operational. Nova head Howard Marner pleads they not destroy Five, but Nova’s security chief, Chick Skroeder, tells his men to use any means necessary to put it out of commission. Newton and his assistant, Ben Jabituya, also search for the robot. Five maneuvers aimlessly, seeking “input.” A security tank catches up as Five crosses a bridge over the Columbia River into Oregon. The tank rams Five and pushes it off the bridge. Five releases its parachute and, unbeknownst to the driver, Stephanie Speck, lands on top of a “Snack Shack” natural foods truck. At home, Stephanie prepares dinner, but notices strange lights going off inside the truck. She finds Number Five, assumes it is an alien from outer space, and welcomes it to Earth. Five audibly responds, “Malfunction. Need input.” Stephanie invites Five to come inside, but the robot does not understand. However, when she says, “forward,” Five comprehends and goes into the house. Five quickly reads every book she has, delighted to have “input.” The next morning, Five is able to imitate the commercials and do impressions of the voices it heard on television. When Five accidently falls off the rear deck of Stephanie’s house, she sees its Nova Laboratories nameplate on its underside and realizes Five is a robot rather than an alien. She telephones Nova, saying she has one of their missing robots and asks about a reward. Nova officials say they will be right over, but in the meantime, she should stay away from Five as it is malfunctioning. Stephanie tells Five that help is coming and that it needs a “tune-up.” Five recites the dictionary definition of “tune-up,” which includes the synonym, “disassemble.” Five sees a grasshopper in the yard and tries to jump like it. However, Five lands atop the grasshopper, squashing it. Five asks her to fix the grasshopper and Stephanie explains death to the robot. Five gets upset realizing that death can also mean “disassemble.” Panicking, the robot gets in Stephanie’s food truck, quickly reads the instruction manual, and drives away. Stephanie jumps onto the truck as it pulls out. Five drives erratically, but Stephanie convinces it to stop just before it drives into the river. When Stephanie asks why Five drove off like that, the robot replies that Nova will disassemble him. When Newton Crosby arrives, Five conveys the message that it is alive and wants to survive. The security team shoots at Five. The robot returns their fire with laser beams, destroying many boats in the marina. Newton gets the security team to stop shooting and powers down the robot. As the security team takes Five away, Newton instructs his assistant, Ben, to go with them and be sure not to erase the robot’s memory. However, once in the back of the van, Five powers itself back up and replaces its damaged arm. When Ben and the driver see Five operating again, they panic and abandon the van. Five drives away, removing the tracking device attached to it. That night, Five returns to Stephanie’s, insisting it is alive. She agrees to let the robot stay the night and later, the two dance together, Five imitating dance moves it observed while watching the movie Saturday Night Fever. The next morning, Stephanie’s former boyfriend, Frank, arrives to collect the $25,000 reward for the robot. Five responds by disassembling Frank’s Trans Am sports car. When Frank fires his shotgun at Five, the robot deflects the bullets and fires its lasers, chasing Frank away. As Newton Crosby searches for Five, Nova chief Howard Marner radios that Stephanie wants to meet with him. Newton goes to the Black Cat Inn, where Stephanie tries to convince him that Five is alive. Newton responds that the robot can seem lifelike, but it is malfunctioning. As they talk, Stephanie realizes that Nova operatives are in the restaurant, waiting to capture Five. Meanwhile, Five is hiding in the woods nearby when the other SAINT robots try to capture it. Five eludes them, then reprograms them to behave like screen comics The Three Stooges. Five goes to the Black Cat Inn and rescues Stephanie from the Nova security team. They drive away together, while the security team chases. They elude their pursuers, then return to the Black Cat Inn where Five kidnaps Newton Crosby. Five insists it is alive and refuses to allow Newton to reprogram it or even look at its wiring. Five says that it is wrong to kill or disassemble. Newton asks how Five knows that and performs various tests on Five, including a Rorschach test. As Five offers human-like responses, Newton is slowly swayed. Finally, when the scientist tells a joke, Five responds with laughter. Newton says that is a spontaneous emotional response and he is finally convinced the robot is alive. Nova security men arrive along with the Army, demanding the robot. They capture Newton and Stephanie, but Five hides in the van. As the men approach, Five dashes out the back and races across the desert. The Army shoots at the robot and a helicopter fires a bazooka at it, destroying it. Devastated by its “death,” Stephanie collapses and Newton tries to comfort her. Howard Marner is devastated by the loss of the valuable robot and fires Newton Crosby and the security chief, Skroeder. As Stephanie and Newton drive away, Five climbs from beneath the flooring in back, explaining that it quickly assembled a duplicate robot out of spare parts in the back of van. Newton mentions they can hide out on the forty acres of land he owns in Montana. Five takes the steering wheel and announces it wants a new name, suggesting “Johnny Five” would be good.