Bill Warren wrote:
Colossus Rex wrote:
On examination, I don't think the sci-fi premise holds up at all.  What Gyllenhaal is able to do on the train... and not just at the end... is counter to everything we've been told via the technobabble exposition the scientist character provides. 
I'm a little confused here.  In time travel stories, everyone is on their own; there are no "laws" regarding time travel.  This is another time travel story, and made up its own rule.  It even made up a rule that it then quite deliberately (and carefully) violated.
The law it sets up at the beginning is that it is NOT a time travel story.  The process involves accessing residual memory, the source code, like a data file.  Hence the repeated warnings to Gylenhaal that he can't affect the outcome, he's just searching for information. 

But this notion is violated as soon as Gyllenhall is able to do anything, or see or hear or feel anything, within that memory that was not experienced by the guy whose memory is being accessed. 

And it's broken big time at the end.  Basically, for no reason that's explained, it has become time travel.  And as Steve points out, there are unanswerable questions about who occupies the body at the end.