In the world of Inception, the military has developed group dreaming as a way of providing a safe space for soldiers to practice killing each other. (Apparently, video games were never invented in the Inception universe.) Group dreaming has led to corporate espionage, with spies doping VIPs and jumping into their brains to rummage around for secrets.
Unfortunately these people have really boring dreams; in fact, the dreams in Inception are unrealistically realistic. The spies walk around crowded cities, and skulk around hotel rooms, and ski around mountaintops, but nothing ever feels like a dream. No one ever meets a girl who is kind of their cousin, but also kind of their first crush, but looks like the Chicken of the Sea mermaid. There are no singing plants or talking animals, no one ever seems to visit their high school (except it's not really their high school, it's like 5000 times bigger and all the hallways end in mist?) or conflates three apartments into one misremembered one. And most importantly, when people group dream, they're never in their underwear, but instead they show up in really expensive looking clothes carrying five or six guns.
Granted, there is one really excellent sequence where the kid from "Third Rock From the Sun" battles hotel detectives in zero gravity. But try to watch two guys in sharp suits floating around punching each other without hearing "You disappoint me, Mr. Anderson," in your head.
Wait, is this The Matrix, or the "Weapon of Choice" video?
And there is a freight train roaring down a trackless city street punctuating an exciting but otherwise familiar car chase as well, but these are surprising exceptions to the disappointingly mundane dream world. One character stands out as singularly nightmarish. The dead wife of our hero Cobb (played by Leonardo Dicaprio's big square head on Jack Skellington's body) is a pretty French woman, whose interactions with everyone else are calmly murderous. Her name is "Mal," pronounced like the Latin word for "evil," in case you had any doubts.
The movie assembles a team of dream thieves to perform one big caper, so that Cobb can safely return to his children. The caper takes place within three nested dreams-within-dream, with a climax lasting--I don't know, 45 minutes? an hour? it's long--that transpires within the time it takes a van to plummet off a bridge. The goal is to pervert the feelings that a corporate heir (welcome back to ugly heartthrob Cillian Murphy) has for his dead father. Is it all a dream, or did this emotional bank job succeed in providing a happy Hollywood ending?