On Halloween eve, four unsuspecting travelers – two couples on a road trip across the country in search of offbeat roadside attractions – find themselves in the backroads of rural Texas. Their adventure leads them to a bizarre, isolated gasoline station that doubles as a museum of oddities and horror, run by the eccentric Captain Spaulding. Intrigued by local lore, they're drawn to investigate the urban legend of Dr. Satan, a deranged surgeon from the town's past said to have performed grotesque experiments. Spaulding, enticed by their interest, directs them to what's purported to be the final resting place of Dr. Satan, setting them on a path far more disturbing than they anticipated.

The group's detour into darkness brings them face to face with the Firefly family, a deeply disturbed and murderous clan who take extreme delight in pain and mayhem, living in a dilapidated farmhouse filled with unspeakable horrors. As night falls, their quest for curiosity transforms into a desperate battle for survival. Trapped in a nightmare, they find themselves part of a gruesome game, with each family member more terrifying than the last. Their initial fascination with the macabre quickly spirals into a harrowing ordeal, challenging the limits of their sanity as they struggle to escape the twisted web woven by their captors. The dream of uncovering a local legend turns into a fight to live through the night.