When a secret military border post falls silent, an army team is dispatched overnight to re-establish contact and safely retrieve the son of the Army Chief of Staff who is posted there.

What they find is so shocking that HQ orders GP506 to be burnt to the ground at dawn - incinerating the evidence. The investigative team are left with just eight hours to explore the maze-like underground tunnels, find their target and uncover the truth. Time is running out, but the terror that has engulfed GP506 has only just begun...