Serial killers are real-life nightmares.

Here are seven little-known killers of the 19th century.

Serial killer Peter Tobin has three known victims: but was this depraved killer also responsible for the unsolved Bible John murders of the 1960s?

John Wayne Gacy AKA "The Killer Clown" raped and murdered at least 33—crimes he died for in 1994. These are the rarely-discussed details of his life.

A con artist killer and his unsuspecting victims.

Think you know everything about the most infamous serial killers the world has ever produced? 

Here's where they go after they're gone for good...

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An inquiry into his sinister activities concluded that he killed at least 215 of his patients.

Belle Gunness lured numerous suitors to her Indiana murder farm, where she killed them in cold blood and dumped their bodies in a hog pen.

Remembering the victims of this brutal murder spree. 

Lock the doors, bar the windows, and read on if you dare.

Get ready, true crime fans. 

You might want to double-lock your doors and windows before watching these...