Et ungt nygift par befinder sig fanget i et netværk af underjordiske huler. Med sin mand såret, er den nye brud tvunget til at finde tilbage til overfladen for at redde hans liv. I processen opdager de en skræmmende sandhed om "nedenunder", de er ikke alene. Noget ondt jager dem.

A young newlywed couple find themselves trapped in a network of underground caves. With her husband injured, the new bride is forced to find her way back to the surface in order to save his life. In the process, they discover a terrifying truth about the "underneath", they are not alone. Something evil is hunting them.