P4. Gruesome Murder cases you've probably never heard of

Dennis Nilsen, who murdered young men and kept their bodies.

Dennis Nilsen terrorized London in the late 70's and early 80's, killing 15 men over a five-year period. Nilsen would pick up young men at bars and take them back to his home. There, he'd strangle or drown them. Once dead, he'd bathe and dress the bodies, according to The International Business Times. 

He admitted to police that he kept the bodies for extended periods of time before disposing of them so that he could have sex with them and talk to them. He is currently serving a life sentence at the HMP Full Sutton prison in Yorkshire, England.