On manoeuvres with their squad in the Scottish Highlands, soldiers Cooper (Kevin McKidd) and Wells (Sean Pertwee) come across the ravaged remains of another military unit. The only survivor, Captain Ryan (Liam Cunningham), is badly injured and unable to explain clearly what happened; nevertheless, the men get a pretty good idea when night falls and they are attacked by unidentifiable wild beasts.

Finding refuge with a family in a nearby house, the owner tells them about werewolves who hunt in the area, and the soldiers begin to dig in, preparing for a big fight. Meanwhile, Ryan begins to undergo some unexpected changes...