This opens things up to plenty of new dangers, including aliens and some seriously hostile cavemen, but not the kind of wholly propulsive, time-tripping fun that might be expected.

As a coherent story, it mostly works. But what you'll walk away admiring most is the film's ambition.

By the time the film has laid all its cards on the table, it is too late to care. [Full Review in Spanish]

A clever concept, brisk tempo, and filmmakers willing to get absolutely nutty when necessary.