A gruesome murder puzzles police; a cryptic message is left behind at the crime scene, but the identity of the killer remains a mystery; promises are broken, and old secrets emerge, breathing new life into the investigation.

A woman's attempt to flee a troubled relationship leads to her demise; police discover a haunting message left behind, but the case goes cold for years until a prime suspect's macabre desire for blood is revealed.

In Great Falls, Mont., police are on high alert after Morris Davis and Suzette Pritchard are brutally murdered just one year apart; one tip will change everything as the police hunt for a killer.

In Allentown, Pa., a serial killer preys on women in the middle of the night; when one woman refuses to be his next victim, the killer goes on a relentless tirade that ends in his own demise.

A young college student vanishes; later, a shocking discovery is made, and townspeople begin to question those they once believed were innocent; before long, the truth rises from the dead of night.

In Baltimore, a predator stalks young women and strikes when they are alone at night; however, one of the killer's victims will turn out to be his worst enemy.

A young woman with a promising future vanishes from her apartment in the middle of the night; family and friends search desperately for any sign of her, but the truth will only come to light after a grisly crime is committed miles away.

Two young mothers living hundreds of miles apart vanish under eerily similar circumstances; years pass without a single lead in either case until a Missouri police officer's routine house call uncovers an unlikely suspect.

In Baton Rouge, La., defense attorney Chiquita Tate is murdered while alone in her office at night; police quickly zero in on a prime suspect until a twisted conspiracy from Tate's past comes to light.

In Bend, Ore., Halloween night ends with a young woman's disappearance; suspicion of foul play runs deep, but her whereabouts remain a mystery; over time, secrets begin to emerge and lead investigators to the least likely of suspects.

After finishing a midnight shift at a local factory, Fred Matting is murdered in his own driveway; his once peaceful neighborhood turns into a living hell as residents fear that a vicious killer is lying in wait for them.

Working the graveyard shift, a convenience store clerk is on edge after a string of murders are committed within blocks of her store; soon, her worst nightmare becomes a reality when she comes face to face with a serial killer.

There's a reason murder investigations don't begin with preconceived notions. Sometimes those least expected to be capable of committing such dark deeds -- respected role models and trusted members of the community -- can have a sinister side. "Unusual Suspects" documents baffling, challenging investigations, actual cases that were anything but cut and dry. Episodes feature in-depth interviews with leading law enforcement personnel combined with stylized re-enactments, illustrating how illusive offenders evaded capture for years before being undone by persistent police work.

Stylized re-enactments tell stories of actual crimes that have a similar moral: choosing to trust someone can be a life or death decision. One moment, the world seems so safe; the next, it becomes completely unrecognizable, all because someone betrays the trust of a family or social circle, leading to paranoia and suspicion and ultimately a cold-blooded murder. The husband, the best friend, the business partner, the stockbroker, the neighbor and the mistress are left looking over their shoulder, living in fear of the killer, or the truth, or being caught in a lie. As the investigation unfolds and secrets are laid bare, it produces a horrific realization: the victim was killed by someone they trusted.

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.

Hundreds of homicide cases in any given year can shake even the staunchest cities and police departments to the core. The statistics, however, don't paint the real stories and the effect that lingers -- through the pain endured by victims' loved ones, the community impact, and the memories that detectives will never forget. "Homicide City" explores unforgettable murder cases from major American cities, investigations that had law enforcement banding together across metropolitan landscapes in a sequence of manhunts. Each story is told by veteran homicide detectives, local reporters, and the victims' families.

Once dubbed "Wonderland" because of its immense summer beauty and grandeur, the rolling mountains and deep forests of the Pacific Northwest become a haven for a series of murders. Using stylized re-enactments and interviews with law enforcement personnel and family and friends of victims, episodes focus on a team of dedicated Portland, Ore., homicide investigators who seek answers to mysterious, disturbing murder cases. In the premiere, Det. Molly Daul realizes she is dealing with a sexual predator, whose chilling confession remains with Molly to this day. The killer then turns his sights on her, raising the stakes even higher.

Co-executive produced by none other than Khloé Kardashian, who knows a thing or two about sisterly bonds and how they can go awry, this series details shocking crimes committed by pairs of sisters. Sometimes the siblings work in concert, but often the duo turn against each other with the deadliest of outcomes. Hourlong episodes recount actual crimes via stylized re-enactments and interviews with immediate family members and close friends, painting a picture of where and why the sisters' lives went wrong. As well, investigators and law enforcement anchor each story as they recount firsthand their unraveling of the case and try to make sense of the crimes committed.

"Accident, Suicide, or Murder" investigates the deaths that are considered just a little bit too mysterious. This hourlong series takes viewers along on an exploration of unbelievable true stories. Each episode retraces the original investigations from the start to the finish. Investigators lead viewers through all of the twists, turns and surprises that crop up as they dissect the red flags, show evidence, and point out the strange behavior that puts everything into question.

The proverb "home is where the heart is" most definitely doesn't apply in this true-crime series, which is set in otherwise quiet suburban residences that become anything but welcoming. The preyed upon believe the walls of their home provide a safe haven, but down dark corridors and behind the veneer of thin glass lurks unimaginable horror. Hourlong episodes paint pictures of tension-filled scenes, adding up to crime stories told via stylized re-enactments. In first-person interviews, viewers hear from family and friends of the victims and law-enforcement personnel familiar with the investigations.

"Betrayed" reveals chilling stories of chasing the American dream and how the veneer can dramatically crumble, ending in murder at the hands of a trusted family member, co-worker, lover, or friend. The cases of deception are told through the lens of the fictionalized, first-person perspectives of the victims. As investigators, family, and friends peel back the layers and facts of each case, the otherworldly narrator already knows where the trail ends. The narrator guides viewers through various relationships, raising suspicions about who will commit the ultimate betrayal.

On the outskirts of Los Angeles lay the city's roughest neighborhoods, the stomping grounds for LAPD Detective Lindy Gligorijevicin in the late 1990s. During that time, the police department's Foothill Homicide Unit investigated hundreds of murders, but only Gligorijevic -- driven by the need to give victims a voice -- earned the moniker "the killer closer." In this series, she revisits her most shocking cases, detailing how she solved them and the ways in which she convinced cold-blooded killers to confess.