King Leonidas of Sparta and a force of 300 men fight the Persians at Thermopylae in 480 B.C.

Decades after a rock church in communist Romania's Carpathians caved when an expedition caused a landslide and buried everyone, Dr. Nicolai's scientific team exploring the associated Templar Knights monster fighting-legend discovers a deep, flooded cave system and hires the brothers Jack and Tyler's brilliant divers team to explore it. Another explosion traps them, after finding a mysterious parasite turning all species carnivore, and later an independently evolved predator species. Jack may be infected and turning, but Tyler sticks with him, so the group splits, hunted by the monsters, which also fly.

In an America wracked by crime and overcrowded prisons, the government has sanctioned an annual 12-hour period in which any and all criminal activity-including murder-becomes legal. The police can't be called. Hospitals suspend help. It's one night when the citizenry regulates itself without thought of punishment. On this night plagued by violence and an epidemic of crime, one family wrestles with the decision of who they will become when a stranger comes knocking. When an intruder breaks into James Sandin's (Ethan Hawke) gated community during the yearly lockdown, he begins a sequence of events that threatens to tear a family apart. Now, it is up to James, his wife, Mary (Lena Headey), and their kids to make it through the night without turning into the monsters from whom they hide.