WHAT I LIKED: Source Code's strongest asset is its clever mystery and the way Ben Ripley's script chooses to reveal its cards as it progresses. At the very start in a rather genius scene in which a man appears to be trapped inside another man's body on an ordinary commuter train which proceeds to explode, we - like our central character - have absolutely no idea what's happening. However, we begin to understand along with him that there's something rather sinister at work here, and it's the confusion and the tension surrounding the unknown - along with the pressing issue of solving the mystery around who bombed the train - that keeps you on the edge of your seat. It's basically a mystery story embroiled in an even bigger mystery story, and the fact we unravel these mysteries along with the central character means we're invested even more hooked, particularly when Jake Gyllenhaal is doing such a fine job with the portrayal.
However, like any good script, it also becomes increasingly clear throughout that the plot is also serving something a little more meaningful to do with the central character. The final moments see him forced to tackle some personal issues rather touchingly, and this handle on the humanity of the character and those he encounters on the train makes for an even more engaging experience.
Couple that with the fact that the film does - at least at times - leave the storytelling to be done visually rather than through dialogue, in the end you've got yourself a great mystery executed fairly well.
WHAT I DIDN'T LIKE: The film equally isn't without its clumsy moves though, as when the script does reveal its cards, there are a few exposition dumps that feel extremely clunky. That's only emphasised by the fact that the reasoning behind the mystery of the character's situation is very bizarre, or that that actually winds up as some pseudo-profound statement about alternate realities as director Duncan Jones milks things for all they're worth. The score is also pretty jarring at times and some of the visual effects are exceedingly awkward, and that ultimately all has the effect of taking you out of what is otherwise quite a captivating movie.
VERDICT: Uneven but generally engaging, 'Source Code' has a clever mystery and a great performance at its centre, but it often stumbles in the revealing of its awkward reasoning.