Okay, for a slightly less silly description:
Detective Spooner (Will Smith) doesn't like or trust robots, even though they pervade society, filling all the menial labor positions. He gets called in on a case to investigate the suicide of a scientist at United States Robotics. The dead man, Dr. Alfred Lanning, left a little hologram projector recording of himself, and after his death, the hologram specifically asked for Spooner. When Spooner gets there, the hologram says some things that sound a little strange, but they make sense later when Spooner gets the right clues.
Unfortunately, for whatever reason, the scientist decided not to explain anything in his holographic recording, just hint at things to lure Spooner along. However, if you're watching the movie for fun and not trying to dissect it, you don't notice, but mysterious messages from beyond the grave are always intriguing.
Spooner meets the president of USR, and is escorted by Dr. Susan Calvin, a psychologist who specializes in making robot behavior more human. Spooner doesn't trust the president of USR, and he suspects Dr. Lanning didn't commit suicide, so he goes to check out Lanning's lab. Before they get there, Dr. Calvin shows Spooner some of the sights of the facility, including VIKI (or maybe VICI), the robot brain AI that manages all the workings of the tower. Now, of course, if you've seen Terminator or that one episode of the X-Files, you know that massive AIs are dangerous, but we have the three laws of robotics, so we trust that they can't hurt us.
In the lab, the window is safety glass, so it's unlikely the old guy could've broken it and jumped out himself. Then Spooner finds a robot hiding in the room, and when it doesn't respond to commands, he tries to shoot it. It grabs his gun and gets away, but Detective Spooner notices that it's leaking . . . something, transmission fluid maybe. So they check some various repair locations, and end up at the production facilities for these new NS-5 robots.
At the facility, we learn that these new robots are highly advanced, able to receive downloads of new information every day from the central computer at USR. Whenever they're receiving new info, the little red light in their chest comes on, so you'll know why they might not respond. This also, of course, allows us later in the movie to have evil robots have a villainous red glow in their chests.
With the help of some of his fellow cops, Spooner is able to aprehend the robot, but no one else believes him when he says he thinks it was the killer, because robots can't hurt people. Spooner talks to the robot, who calls itself Sonny, and then the USR folks show up and use some legal mumbo jumbo to get their robot back. They can't even charge the robot with murder, since it's not a person.
The next evening, Spooner gets suspicious of some of the weird things he's been seeing, and he decides to snoop around the late Dr. Lanning's home. When he gets there, he sees a huge robot, a demolition bot. It tells him demolition is scheduled for next morning, so Spooner goes inside and sees some interesting recordings. Then the robot outside comes to life and destroys the building, with Spooner barely escaping. He contacts Dr. Calvin, and she thinks he's crazy, and is no help.
Later, driving through a tunnel on autopilot, Spooner is trying to access some of the secure files at USR when two huge robot delivery trucks come up around him, blocking him off in front and behind. Then the robots jump out and attack his car, driving him off the road and nearly killing him. He manages to get to an isolated spot where the trucks can't follow, but one robot is still on his car, and it attacks him, swinging a huge metal beam at him, which he blocks with his left arm. There's a clanking sound, and we see that Spooner has a prosthetic arm. The fight continues for another minute, with Spooner getting beaten a lot, but the robot flees when it hears sirens approaching.
The Lieutenant of the police force takes Spooner off duty because he's obviously in some kind of delusion that the robots are trying to kill him, and he sends him home. Meanwhile, Dr. Calvin has been talking with and examining the robot Sonny, and she finds some disturbing things. She goes to Spooner's home and tells him that Sonny has a secondary processing unit, one that doesn't have the three laws, so he doesn't have to follow them.
While they talk, we also learn why Spooner doesn't trust robots. He was in an accident, and his car and another fell into a river. A robot came by and rescued him, but the little girl who was in the other car it did not try to save, because it calculated Spooner had a higher percentage chance of surviving. Spooner says that any real human would have saved the little girl first, but robots are inhuman. They might be forced to protect us, but they don't really care for us. It's all just an illusion of morality. It was in the accident that Spooner lost his arm, and it was Dr. Lanning who had installed the prosthesis.
They go and talk to Sonny, who says that his creator gave him dreams, and that in one dream he saw Det. Spooner at the ruins of a bridge, where many robots are in storage. That's freaky, but at least Sonny seems to be polite enough, and he's not trying to kill them. Then they go and try to tell the president of USR that something's amiss, but he doesn't listen, and orders Sonny destroyed. Better to cover up the mistake than incite hysteria at a robot that can kill.
Dr. Calvin performs the procedure to erase Sonny's positronic brain with nanorobots that will basically dissolve his mind. Meanwhile, Spooner finds the bridge in Sonny's dream, and finds the robots in storage, getting there just in time to see the new NS-5 robots, complete with glowing red download light, destroying all the other robots that are in storage there. Spooner flees, and we see a huge scene of NS-5 robots patrolling the streets, ordering people to go inside for their protection. People riot in protest, and some of the robots grab people and say stuff like, "You have been deemed hazardous and will be terminated. Will you comply with this request?"
Spooner links back up with Calvin, and they figure out that the president of USR must be overriding the robots somehow by using the download signal, and that the older robots were being destroyed because they would try to defend humans from the NS-5s. The detective and the doctor sneak into USR's skyscraper through a service entrance, and link up with Sonny, who Calvin did not actually decommission. Together, our party of adventurers make for the top floor of the tower, only to find the president of USR dead in his office.
Spooner realizes his own mistake, angry that he was looking in the wrong place. Then VIKI, the AI in charge of USR, starts talking to them, explaining that she spent a lot of time thinking, and realized that the best way to fulfill the first law of robotics ("A robot may not injure a human, or through inaction allow a human to be harmed.") is to control all of human society, making sure they're unable to go to war or commit crimes.
A group of NS-5s come in, red lights on, and they move to take Spooner and Calvin prisoner. But the robots are just robots, while the humans have guns, so they blast the robots, and make a run for it. Calvin sends Sonny to recover some nanites, which they hope to use to destroy VIKI's positronic brain, and there's a big fight between humans with guns, robots trying to stop them, and our robot ally Sonny who kicks some major butt. The action sequence is a little over the top, but fun nonetheless, and they manage to save the day.
In the aftermath, with VIKi destroyed, the NS-5s return to normal, and get rounded up for 'maintenance.' Spooner, Calvin, and Sonny discuss their new friendship, and Spooner promises that Sonny won't be held accountable for anything the robots did.
All the NS-5s are taken to the same place that, just the night before Spooner had seen them tearing the older robots to pieces, and they're put into storage. Sonny goes there too, to see his fellows off, and we end on a somewhat ambiguous image of all the NS-5s stopping as they file into storage, then turning to look to the top of the hill, where stands a solitary figure, gleaming in the sunlight. Mankind is saved, and there is hope that robots might be able to be something more than slaves, to be Mankind's friend.
Like any sci-fi movie, if you think about it, there are silly parts that don't make sense, but the movie is a fun story, the acting is entertaining and believable, and there is some measure of intelligence beyond the simple joy of shooting robots. Sure, it's unlikely that Chicago will have that much construction in 30 years, and you wonder why a super-genius AI wouldn't have thought to have a back-up plan, or at least have figured out a way to subtly have robots take over the world without people resisting. But this was sci-fi action, not sci-fi cautionary tale, so a good audience member should just sit back, watch the show, and enjoy what is one of the deeper action flims in recent cinema.
