The Demonists2 books in series
The Demonists Publisher's Summary
It was supposed to be a simple exorcism, a publicity stunt to firmly establish John and Theodora's thriving paranormal investigation empire in the public eye. But something went wrong, leading to an on-air massacre that unleashed a malicious host of demons and left Theodora catatonic, possessed by countless spirits.
John sets out on a desperate quest to find a cure for his wife, but his obsession brings him face to face with an even more terrifying problem: Theodora's possession is only one piece of a deadly plot that is threatening the entire world. An ancient evil is about to make Earth its battlefield, and without John and Theodora's intervention there is no chance for salvation.