Dark Deity - Asylum Series, #3

Some spirits never rest in peace.Paul Mahan escaped the terrifying evil that dwelled in the Rookwood Apartments. But others have not been so lucky. Young Ella Cotter, an innocent child, finds herself tormented by a ghost Paul unwittingly freed when he escaped the building's haunted grounds. As Paul attempts to use hypnosis to separate the child from the tortured entity that clings to her soul, blood runs in the streets.
A series of mysterious killings rocks the nearby city of Tynecastle. And Paul is convinced the violent incidents are linked to Dr. Palmer, a sadistic wraith, who once turned Rookwood into an asylum of horrors. Working with the local police, and a rare book dealer with an interest in the occult, Paul and his allies soon find themselves face to face with an enemy unlike anything they have ever imagined.
This terrifying evil force grows more powerful with each victim it kills. And the only way to stop it may cost Paul his mortal soul.