The Secret in Their Eyes (El secreto de sus ojos)

I was utterly enthralled by the story, both the past and the present. We debated the events depicted in the film the whole ride home. The Secret in Their Eyes leaves you with countless implications, and lets you sift through them until you, like the main character, arrive at the inescapable truth (although ymmv).

In short, it's good. It's complicated. Go see it. :)