Dr. Gene Tuskin works with troubled children, perhaps none more troubled than Regan MacNeil, who suffers from bad dreams and repressed memories. The memories she represses are of the time she was possessed by a demon. Dr. Tuskin's invention, a device that hypnotizes two persons and links their minds together, reveals that the demon, named Pazuzu, still lurks within her. It is desperate to emerge again and wreak havoc. Meanwhile, Father Philip Lamont is ordered by his cardinal to investigate the death of Father Merrin, the priest who died while performing an exorcism on Regan. Father Lamont undertakes his task reluctantly. He feels unworthy of his assignment. He also feels that Evil is literally an entity and that this entity is winning the battle over Good. His investigation takes him to Africa where he locates another recipient of Merrin's exorcising and learns something fascinating and terrible about locusts.

In the distant future Earth is divided into two camps, the barely civilized group and the overly civilized one with mental powers. A plague is attacking the second group, after which its members cease to have any interest in life and become nearly catatonic. When Zed, one of the barbarians, crosses over, the tenuous balance in their world is threatened.

Mal Reese is in a real bind - owing a good deal of money to his organized crime bosses - and gets his friend Walker to join him in a heist. It goes off without a hitch but when Reese realizes the take isn't as large as he had hoped, he kills Walker - or so he thinks. Some time later, Walker decides the time has come get his share of the money and starts with his ex-wife Lynne who took up with Reese after the shooting. That leads him on a trail - to his wife's sister Chris, to Reese himself, then onto Big Stegmam, then Frederick Carter and on and up the line of gangsters all in an effort to get money from people who simply won't acknowledge that he's owed anything.