It's a post-apocalyptic world and parents Ray (Alexander Skarsgård) and Claire (Andrea Riseborough) are hidden away in a bomb shelter with their preteen daughter Zoe (Emily Alyn Lind). We see them struggle with issues like depleted rations (a rat has burrowed into their canned goods) and hear lots of talk about the dangerous "breathers" who roam at ground level.
Most of Hidden simply waiting for something to happen. There are no scares, at least not until the rather abruptly-arriving climax, so don't make the mistake of assuming this is a horror film. That's the genre Warner has chosen for marketing purposes, but it's really for lack of a better fit. This talky film is more of a sodden drama. Ray, Claire, and Zoe aren't interesting enough characters to add any psychological depth or insightful examination of being isolated from "normal" society (which apparently no longer exists after a deadly disease epidemic).
There's a big twist for those who stick it out to the very end. Sort of a sub-M. Night Shyamalan surprise. But it's simply not good enough to justify spending the hour-and-a-half that proceeds it. The Hidden DVD has been issued without even the simplest of bonus features (they didn't even bother to put in a chapter index). Hidden probably should've remained hidden in the vaults.