Three rebellious friends, Mike, Geoff and Frankie, are desperate to avoid a school field trip to Wales. Martin, the school nerd, helps them hide away in an old underground bunker and his only condition is that his friend Liz joins them. The teenagers party, uncontrolled and undetected in the soundproof bunker hidden deep in the woods. But when Martin doesn't return to let them out the party atmosphere drains and their sanctuary quickly becomes their living nightmare.