Ultimately, Source Code makes good on its Hitchcockian opening sequence -- it may pale in comparison to the master, but it's a fun, puzzle-filled ride, with excellent pacing and a mounting uneasiness that recalls the best episodes of The Twilight Zone.

Source Code is a sci-fi thriller that simply shouldn't work as well as it does.

It's this emotional arc underlying the ticking-time-bomb plot that keeps the movie from succumbing to its flaws.

What unravels and untwists in its repeated eight minute episodes, makes for an extremely compelling, original, and thought-provoking thriller.