The Children of Red Peak by Craig DiLouie

They escaped the cult, but are they free?
 

David Young, Deacon Price, and Beth Harris live with a dark secret. They grew up in an isolated religious community in the shadow of the mountain Red Peak, and they are among the few who survived its horrific last days.
 

Years later, the trauma of what they experienced never feels far behind. And when a fellow survivor commits suicide, they reunite to confront their past and share their memories of that final night.
 

But discovering the terrifying truth might put them on a path back to Red Peak, and escaping a second time could be almost impossible….