A quadruple murder rocks a small California town, leading police to investigate a refugee camp run by a local man; what appears as a quiet, small community soon reveals itself as a sinister group full of manipulation, abuse and violent rituals.

A family is desperate to find a daughter who ran off with a strange cult; years later, police are called to a posh mansion near San Diego and are shocked to find 39 bodies in a mass suicide.

Police investigating a 911 call for a suicide interview the victim's girlfriend, who claims there's more behind his death; police must determine if an online cult that believes in aliens and reptiles disguised as humans is actually at fault.

To his followers, he's an angel who died and came back to life, but when seemingly accidental deaths keep occurring around him, one investigator digs deeper.

After three obedient followers die during an intense sweat lodge ceremony put on by a prominent self-help guru, police must determine if their deaths were accidental, or did the guru push the participants too far.

After crossing the Mexican border from Brownsville, Texas, a student out on spring break goes missing; the investigation leads US officials to a cult known for practicing witchcraft led by a former male model and a high school cheerleader.

After hearing about a religious cult stockpiling weapons on an isolated farm outside Rulo, Nebraska, FBI agents cultivate an informant from inside the group who details the torture and murder being ordered by the group's diabolical leader.

Police in Kirtland, Ohio receive a tip about a family of five killed and buried in a barn belonging to a local cult; as they question the cult, investigators learn even more sinister details of power and manipulation leading up to the murders.

Jennifer Wendorf comes home to find her parents brutally murdered and sister missing; searching for answers, investigators discover a complicated web tracing back to a cult of self-proclaimed vampires.

The Gatekeepers saw themselves as pure participants in a religious quest to cleanse the world; when a member challenges the cult's radical leader, cops discover how he paid for his disobedience with his life; now his killers are nowhere to be found.

A community is shocked when a prominent local doctor is gunned down by two mysterious women in broad daylight; Murray, Utah, police uncover a web of warring prophets, strained families and multiple murder plots.

Investigation Discovery joins forces with reporters from People magazine to tell stories of the destructive effects cults have on members and their families. Lured by false promises, everyday people are caught up in terrifying webs of abuse, deception and manipulation, building to pivotal moments when blind worship leads to violence and even death. Each hourlong episode offers an in-depth exploration of a twisted American cult, from world-famous Jonestown to smaller but equally disturbing sects of depravity. People's journalists interview survivors who managed to escape a cult, exposing stories of power-crazed leaders who use mind control, sex, and daily rituals to dominate followers.

In 1969, Tony Alamo and his wife, Susan, founded the Alamo Christian Foundation in Los Angeles, beginning careers as born-again, fire-and-brimstone televangelists. Attracting hippies and other discontented youth, the foundation soon evolved into a cult that is said to still be in operation. By avoiding law enforcement and maintaining a strict code of silence among followers, the Alamos gained immense power, becoming millionaires on the backs of their congregation. This four-episode docuseries shines a light on the Alamo empire through rarely-seen archival footage, including an exclusive videotaped deposition with Alamo himself. It also features interviews with the FBI agent who took Alamo down as well as cult survivors who have never previously shared their stories.

There are manipulators in the midst, scheming right under everyone's noses. Even with people trusted the most, there may be something sinister lying beneath the surface -- a plot set in motion by someone close with a deadly motive. This true-crime series tells stories of actual murders committed not by strangers but by someone the victim knew, someone hiding in plain sight, or someone leading a double life. These wolves in sheep's clothing use deception as a weapon to try to get away with murder.

"Accident, Murder, or Suicide" investigates the deaths that are just a little bit too mysterious. It explores the unbelievable true stories in this hourlong program. Each episode retraces the investigation from the start to the end. Investigators take viewers through the twists, turns, and unexpected surprises as they dissect the red flags, show evidence, and point out the strange behavior that puts everything into question.

"Deadly Demands" profiles actual hostage situations, blending audio from negotiations with witness interviews to offer in-depth looks of the heightened emotions endured during terrifying standoffs. Episodes detail complex relationships between hostages and takers, and as the situations unfold, viewers hear every shocking moment via the negotiation tapes. Further insight is provided into quick-thinking, calm-under-pressure men and women who use years of training to get inside the minds of hostage takers -- and to save innocent lives.

Crimes and mysteries are investigated.

"Dateline," NBC's long-running newsmagazine series, brings its cutting-edge, heavy-hitting journalism style to Investigation Discovery, bringing viewers harrowing crime stories and tackling topics of broader importance to society. Hosted by either Lester Holt or Keith Morrison, the repackaged episodes go behind the headlines to introduce the detectives, the suspects, the victims, and the families involved in a devastating criminal investigation. Emotions play out in a courtroom, where dark secrets are laid bare until a verdict is revealed.

Powerfully emotional stories tell of people who have been targets of compulsive stalkers. According to the Centers for Disease Control and Prevention, more than 6 million people in the U.S. are stalked each year, and in most instances, the stalker is someone the victim already knows. The series' hourlong episodes dramatize actual cases through visceral re-enactments and pointed testimony of victims, family members and law enforcement authorities, revealing what happens when stalkers can't have what -- or who -- they want, and stop at nothing to ensure that no one else can either. The chilling accounts probe the mechanics of an obsessive mind and the devastating impact of delusion.

Raw, unbridled and chilling depictions of human desires surface in "In Ice Cold Blood." True crime is depicted at another level as Ice-T takes viewers straight into the stories. Money, sex, lust, and greed run rampant with very real consequences. Family members, friends and detectives recount each case -- a missing military veteran, a student murdered in a crime of passion, and secret payouts are only some of the cases. These stories are told through re-enactments, in-depth interviews and archived footage.