The plot is complicated, so I'll just give you the basic premise. Leo is in the business of going into people's dreams and stealing information. Things get a little more crazy when he tries to pull off Inception, or planting an idea in a persons mind while they are sleeping. Let the complexity and mind boggling effects begin.
Really, it's an extremely well made movie, and it's exciting the whole time....even when you don't have a clue whats going on. The best part is, it doesn't feel like a copy of any other movie. It took the director about 10 years to write the thing. Honestly, I don't know how he wrote it, or how he got the actors to understand it and star in it. At any rate, GO see this movie. Oh, and don't worry if you miss the previews. They were all pretty terrible, including a new stinker from M. Night Shyamalan. Close your eyes during that one, otherwise you might try and kill yourself and miss out on this years best movie so far.