Dom Cobb (Leonardo DiCaprio) awakens on a sea-soaked beach with a Japanese security officer poking him with a rifle. And then he’s a prisoner inside the lavishly Oriental fantasy chambers of a wizened plutocrat. And then he’s dressed to the nines and cutting deals with a younger tycoon, a Mr. Saito (Ken Watanabe). And then there’s a mob hurling Molotov cocktails outside a hotel room where Cobb and his associates are wired to Saito in his dreams. And then they are speeding away on a bullet train. And then a gunfight erupts inside the Oriental fantasy house. And then, and then and then…

Inception, the latest film by Christopher Nolan (The DarkKnight), goes on and on like that. DiCaprio plays Cobb as a noirish private dream detective, a spy for hire in the more infernal regions of corporate espionage. His job is to steal secrets by entering and manipulating the dreams of his targets—until Saito makes him an offer he can’t refuse. The tycoon will fix the legal problems that prevent Cobb from returning to America if the nocturnal sleuth successfully plants destructive ideas in the dreams of his rival at a British corporation vying for control of the global energy market.

It sounds fascinating, and yet it’s not. The logic of dreams Nolan tries to replicate by jumping between scenes and settings would benefit from more surrealism and less computer-generated pyrotechnics. And since, like a mediocre sci-fi flick, Inception insists on explaining every step by reference to convoluted science cooked up for the occasion, much of it between Cobb and his youthful new sidekick with the mythic name of Ariadne (Ellen Page), it’s little wonder that the movie drags along for nearly two-and-a-half hours. In The Matrix, probably an inspiration for Inception, the necessary explanatory words clocked by at turbo speed, seamlessly integrated into the action. And the stakes were much higher in The Matrix, which questioned the nature of reality itself. By contrast, Inception is more of a quasi-intellectual puzzle without much heart or soul.

A performance as wildly over the top as Heath Ledger’s in The Dark Knight could have elevated Inception. DiCaprio’s protagonist manages only to look like a morose gumshoe on an assignment he wished would soon end.