The Gloucester House of Horrors...
Once upon a time in England, there was a warped family called the Wests. Little Fred was the second in the line of children, but from the sounds of it, he wasn't the only twisted one. His father and mother sound pretty sick, too. (Then again, maybe Fred made it all up.) Whatever the circumstances of his youth, though, Fred West became a serial killer and eventually found himself the perfect bride to participate in his madness.
They say the killings started in 1967 - I mean, if you don't count the little boy Fred ran over with an ice cream truck in 1965. I tried to follow along in the path of killings, but the bastard's proclivity for violence and his inability to keep it in his pants led me to a great deal of confusion. Let's just say he spent a lot of time raping and murdering, even before he met his wife.
Now, Rosemary (Rose) wasn't one of those women who marry a serial killer and then are all like "I had no idea". Not only did she know, she participated. In fact, she murdered Fred's step-daughter while he was away in jail for another crime. I won't go into great detail about their demented relationship. Suffice it to say, Rose enjoyed a steady income from her prostitution, and Fred enjoyed watching.
When they were finally caught, it was because the police were looking into accusations Fred had raped one of his daughters. That's when the authorities noticed one of his other daughters was missing. According to reports, the other children had been told on numerous occasions that they'd better behave or they'd end up under the patio like Heather. This prompted them to dig up the patio area. Expecting to find only Heather, they discovered several other bodies as well.
After they'd excavated that home and a previous dwelling the family had called home, they had 11 bodies total. Later, they found one more and added that to Fred's charge. Rose was charged with 10 murders.
Fred, the bastard that he was, hung himself while he was awaiting trial. Rose stood alone and was convicted of those ten murders.
The authorities aren't really sure, though, if those are the only ones. They say the Wests committed murder from 1967-1987, but since they weren't apprehended until 1994, I'm betting there are other bodies the police don't know about or that haven't been attributed to this sick couple.