Shadow People (Peter Warlock Series)

In Shadow People, national bestselling author James Swain's brilliant follow-up to Dark Magic, magician Peter Warlock has a dark secret. A psychic who peers into the future, he is able to use the information to alert the authorities to pending trouble. During a séance Peter is confronted by a group of evil spirits called shadow people, beings who have the power to kidnap a person's soul. Peter is taken to another plane, where he confronts a serial killer about to claim his next victim. It's a harrowing encounter that Peter only barely manages to survive.
The shadow people aren't done with Peter. They ransack his brownstone and terrify his girlfriend, then go after his friends. Peter realizes that the shadow people are connected to the serial killer, whom he has nicknamed Dr. Death. He also learns that Dr. Death is a member of the Order of Astrum, a group of evil psychics who murdered his parents years ago.
Peter has only a few days to help the police figure out Dr. Death's identity before the serial killer claims his next victim.