The Killer Within

At just 14 years old, Kim Edwards and Lucas Markham sent shockwaves around their small Lincolnshire town in 2016 when they brutally stabbed Kim's mother and sister to death as they slept in their beds.

Detectives reflect on the case of Rodrigo Hernandez, known as the 'Grand Rapids Killer', who confounded police when he murdered stranger Susan Verstegen while she was working in a Texas supermarket.

Ahmed Al Khatib murdered his wife, mother-of-three Rania Alayed, in 2013 and later blamed his actions on the influence of evil spirits, but the sentencing judge concluded otherwise.

Though described as charming by others, detectives saw a dark side to Shawn Grate when they found the remains of two women in his Ohio home and rescued a missing woman he had kidnapped.

The story of nurse Charles Cullen, who confessed to using lethal overdoses to murder dozens of patients during his decades-long career at hospitals across New Jersey and Pennsylvania.

Antoinette Frank was trusted to protect the community as a police officer but ended up committing one of the worst crimes imaginable when she took three lives during an armed robbery.