The Bad Place - Dean Koontz (1990). It was as good as I remember!
Frank Pollard wakes up in an alley at night, filled with confusion and fear. He knows nothing but his name, and that he must escape fast, or else he will be killed. Pursued by a mysterious assailant, Frank barely escapes with his life.
Every time he goes to sleep, he wakes up to find evidence of bizarre nighttime travels which he cannot remember. Afraid of his own actions, Frank enlists the help of husband-wife security team, Bobby and Julie Dakota. At first, the case merely seems absurd, but as they track deeper into the life and past of the mysterious Frank Pollard, the Dakotas uncover an increasingly bizarre and dangerous world threatened by a madman who thirsts for blood.
It is ultimately revealed that Frank Pollard is the brother to the mysterious madman as well as twin sisters. They were born from a mother who was the product of an incestuous relationship. Her father was a hallucinogenic drug-abuser and her mother was his sister. She is a hermaphrodite and impregnated herself with her own seed. As a result of this compounded inbreeding, Frank and his siblings developed unusual psychic abilities. Frank, wanting a normal life, tries to escape from his family while being pursued by his brother who seeks to either bring him back or kill him, and nothing will stand in his way. After a message from Julie's younger brother, who has Down Syndrome and possesses minor psychic ability himself, Bobby, Julie, Frank and his family begin speeding into a final confrontation.