The Alienist meets The Exorcist in Tallis' novel of psychological suspense, as an ambitious young doctor explores the dangerous border between science and the supernatural.

1873. When the ambitious Doctor Paul Clément takes a job on the island of Saint Sébastien, he has dreams of finding cures for tropical diseases. After witnessing the ritualistic murder of a young boy who was allegedly already dead, he is warned never to speak of what he has seen. Back in fin de siècle Paris, Paul's attention turns to studying the nervous system and resuscitation through electricity. Paul is told of patients who apparently died and were brought back to life, claiming to have witnessed what they believed to be Heaven while they lay between life and death. Using forbidden knowledge he swore never to use, he attempts to experience what everyone else has seen, but something goes horribly wrong. When Paul returns to the land of the living, is it possible that he could bring something else back with him, an unspeakable evil so powerful it can never be banished?