In the early hours of March 2015, the police receive a call from a nurse at a provincial Danish hospital. She suspects her colleague is deliberately killing patients and fears that it has just happened again. Soon, several witnesses reveal that they too suspect the same nurse of poisoning patients; some have been harboring their suspicion for years… so why has no one done anything about it before? And now that those patients’ bodies have long been cremated, where is the evidence?

After his December 2003 arrest, registered nurse Charlie Cullen was quickly dubbed "The Angel of Death" by the media. But Cullen was no mercy killer, nor was he a simple monster. He was a favorite son, husband, beloved father, best friend, and celebrated caregiver. Implicated in the deaths of as many as 300 patients, he was also perhaps the most prolific serial killer in American history.

Colorado, 1976. When Reverend Mike Fuller and his beautiful wife, Sharon, arrive in the sleepy town of Rocky Ford, local residents think something’s off about the new couple. The God-fearing minister is gruff and cold, while charismatic Sharon has her husband wrapped around her finger.

Joyce Aparo seemed to be the perfect single mother. She doted on her sixteen-year-old daughter, Karin, encouraging her musical ability and lavishing affection on her. But behind closed doors, Joyce was a terror. For thirteen years, she beat Karin savagely and demeaned her relentlessly. When Karin met the troubled yet brilliant Dennis Coleman, the two fell head-over-heels. But Joyce disapproved—so she had to die.

In 1911 two British heiresses, Claire and Dora Williamson, read a brochure about a revolutionary fasting treatment that promised a lifetime of good health. The sanatorium in the village of Olalla, west of Seattle, was surrounded by a beautiful forest, sparkling waters and fresh air. The sisters agreed it sounded perfect and exactly the restorative holiday they needed. But within a month of arriving, under the supervision of Doctor Linda Burfield Hazzard, Claire and Dora began to realise the frightening truth – they were not patients but prisoners at the isolated sanitorium.

For years, Eddie Lee Sexton ruled his large family like Charles Manson. The depraved patriarch dominated his ragged brood of twelve children mentally, physically, and sexually, and enforced every cruelty imaginable, from vicious beatings to raping his daughters and fathering their children. Finally, in 1992, Sexton's eighteen-year-old daughter Machelle, seeking refuge in a women's shelter, revealed the shocking, sordid details of her father's abuse to authorities. As the law attempted to catch up to Eddie Lee Sexton, he moved his family to a mobile home in western Florida.

In Northampton, Massachusetts, at the Veterans Affairs Medical Center, Kristen Gilbert was known as a hardworking, dedicated nurse - so why were her patients dying? So many emergencies and sudden deaths occurred while Kristen made her rounds on Ward C that her colleagues jokingly called her the "Angel of Death".

On the morning of July 18, 2014, 41-year-old Florida State law professor Dan Markel dropped his boys off at preschool, hit the gym, and headed home to his quiet, tree-canopied neighborhood. Within seconds of pulling into his garage, two .38-caliber bullets fired from point-blank range were lodged in his brain. His brutal slaying defied explanation.

It was a crime that shocked the country. On March 21, 2011, two young saleswomen were found inside a lululemon athletica store in Bethesda, Maryland, one of the nation's wealthiest suburbs. Jayna Murray, thirty, was dead—stabbed, slashed, and struck more than 300 times. Brittany Norwood, twenty-eight, was alive—tied up on a bathroom floor, her clothing ripped, her face bloodied. This is the full true story of what happened.

Best friends Daryl Barber and James Boucher were responsible, and their parents trusted them to spend Spring Break at Daytona Beach unchaperoned. When the boys missed their agreed-upon daily check-ins, their parents were disappointed. When they failed to come home on their planned return date, their parents were terrified. They could not have known that their innocent sons would encounter two violent men on the Florida coast. They could not have imagined the torture their children would endure before their bodies turned up four months later in a Florida swamp.

Gosnell is the untold story of America's most prolific serial killer. In 2013, Dr. Kermit Gosnell was convicted of killing four people, including three babies, but is thought to have killed hundreds, perhaps thousands more in a 30-year killing spree. ABC News correspondent Terry Moran described Gosnell as "America's most prolific serial killer".

David Miller had a dream job and a beautiful family. But one perfect life wasn't enough. So he pretended to be an attorney, then a CIA agent. And he secretly married another woman. He juggled it all quite well—until the day his two wives found out about each other. Miller groped for ways to hold on to his finances and reputation. But when he tried using a gun to silence his second wife, his carefully constructed façade of power and wealth exploded.

After Hurricane Katrina struck and power failed, amid rising floodwaters and heat, exhausted staff at Memorial Medical Center designated certain patients last for rescue. Months later, a doctor and two nurses were arrested and accused of injecting some of those patients with life-ending drugs.

Sharon Marshall was a brilliant and beautiful student whose future was filled with promise—until her murderous, fugitive father drew her into a lifetime of deception that became one of the most baffling cases in the annals of American true crime.

William Neal, who called himself "Wild Bill Cody," was seductive and skillful at separating love-struck women from their money, and ultimately, their lives. Apprehended by police, Neal, who proclaimed himself “better than Ted Bundy,” pleaded guilty to three murders then insisted on representing himself at his death penalty trial. But the psychopathic killer found himself up against the incredible courage of his one surviving victim.