Hoping to sell a diamond ring to fund a holiday, a couple post an ad online. The transaction becomes a home invasion when assailants show up at their door.

While visiting his girlfriend's family on Christmas Eve, 25-year-old Clevee Chick is gunned down by two men who knock and open fire.

Maryland paramedics rush to the scene of a single-vehicle accident and find 20-year-old Brian Moses behind the wheel with multiple stab wounds.

Kelli Underwood relocates to a small town north of Dallas, but her fresh new chapter comes to an end with a knock at her door.

Eighty-eight-year-old Gerald is grateful for a caregiver who takes control of his affairs. He stops communicating with family and disappears without trace.

Chilling true-crime tales of unsuspecting individuals whose lives are forever altered when a stranger knocks on the door.

Chilling true-crime tales of unsuspecting individuals whose lives are forever altered when a stranger knocks on the door.

Chilling true-crime tales of unsuspecting individuals whose lives are forever altered when a stranger knocks on the door.

In a slow real estate market, IBM executive Diane Holik is particularly thrilled when a stranger knocks at her door, offering to buy her Austin home for cash. But it's a trap. And her lifeless body is later found in an upstairs bedroom.

A man dressed as Santa guns down an LA family on Christmas Eve and burns their house to the ground. And when a coroner's report connects the massacre to a bizarre crime scene across town, the terrifying scope of killer Santa's plan is revealed.