The Ruins follows two American couples enjoying a pleasant, lazy beach holiday together in Mexico. On an impulse, they go off with newfound friends in search of one of their group, the young German who, in pursuit of a girl, has headed for the remote Mayan ruins, site of a fabled archeological dig.

Professor David Ullman's expertise in the literature of the demonic - notably Milton's Paradise Lost - has won him wide acclaim. But David is not a believer. One afternoon he receives a visitor at his campus office, a strikingly thin woman who offers him an invitation: travel to Venice, Italy, witness a "phenomenon", and offer his professional opinion, in return for an extravagant sum of money. Needing a fresh start, David accepts and heads to Italy with his beloved 12-year-old daughter, Tess. What happens in Venice will send David on an unimaginable journey from skeptic to true believer....

When Mouse’s dad asks her to clean out her dead grandmother's house, she says yes. After all, how bad could it be? Answer: pretty bad. Grandma was a hoarder, and her house is stuffed with useless rubbish. That would be horrific enough, but there’s more - Mouse stumbles across her step-grandfather’s journal, which at first seems to be filled with nonsensical rants...until Mouse encounters some of the terrifying things he described for herself.

Lifestyle journalist Katrine escaped past traumas by moving to a coast renowned for seaside holidays and natural beauty. But when a vast hoard of human remains and prehistoric artifacts is discovered in nearby Brickburgh, a hideous shadow engulfs her life. Helene, a disillusioned lone parent, lost her brother, Lincoln, six years ago. Disturbing subterranean noises he recorded prior to vanishing, draw her to Brickburgh's caves. A site where early humans butchered each other across 60,000 years. Upon the walls, images of their nameless gods remain.

During the overthrow of the Mexican government, Beatriz’s father was executed and her home destroyed. When handsome Don Rodolfo Solórzano proposes, Beatriz ignores the rumors surrounding his first wife’s sudden demise, choosing instead to seize the security that his estate in the countryside provides. She will have her own home again, no matter the cost. But Hacienda San Isidro is not the sanctuary she imagined. Something is wrong with the hacienda. And no one there will save her. Far from a refuge, San Isidro may be Beatriz’s doom.

Joe works at a facility that performs human experimentation. His work just followed him home. The government wanted to unlock hidden abilities in the human mind. They put subjects in extreme sensory deprivation. All the test subjects went violently insane. But the research continued. Today it has been perfected. Almost perfected.

Episode Thirteen takes them to every ghost hunter's holy grail: the Paranormal Research Foundation. This brooding, derelict mansion holds secrets and clues about bizarre experiments that took place there in the 1970s. It's also famously haunted, and the team hopes their scientific techniques and high tech gear will prove it. But as the house begins to reveal itself to them, proof of an afterlife might not be everything Matt dreamed of.

Claire Kovalik is days away from being unemployed—made obsolete—when her beacon repair crew picks up a strange distress signal. With nothing to lose and no desire to return to Earth, Claire and her team decide to investigate.

In a boarded-up house on a dead-end street at the edge of the wild Washington woods lives a family of three. A teenage girl who isn’t allowed outside, not after last time. A man who drinks alone in front of his TV, trying to ignore the gaps in his memory. And a house cat who loves napping and reading the Bible. An unspeakable secret binds them together, but when a new neighbor moves in next door, what is buried out among the birch trees may come back to haunt them all.

After the loss of a child along with a slew of agonizing misfortunes, Nick and Jess decide to end their lives. Unable to cope with the misery that fills their days, they commit one last act together and die in loving relief. But when Nick wakes up, he soon realizes that death isn't the gentle darkness he expected. Panicked and horrified, he struggles to understand the twisted abominations and hellish world he's now trapped in.