Bedlamite (2016)

A brother and sister looking to recapture their youth, decide to explore an abandoned WW1 bunker deep in the heart of the British countryside. What they find inside will change their lives forever when the pair stumble across a girl nailed to a chair, beaten, gagged and barely alive. When the captor returns to finish the job the three must frantically try to navigate the many bunker tunnels in a hope to escape the terror. But the man chasing them is the least of their worries.