Paul (Joel Edgerton),
his wife Sarah and their teenage son Travis,
live in a cabin in the woods during a seemingly post-apocalypse, the
unseen outside world having apparently been ravaged by a deadly virus. Their
survival depends on a set of airtight rules, which is made clear from the
offset when they are forced to shoot dead and then burn Sarah's father having discovered he is infected. But when stranger Will tries to break in one night, Paul is forced to make some new rules.
