A young girl brutally murders her parents in their home. The scry map sends John and Chas to in Birmingham, Alabama to work the case.
At the scene of the crime, John runs into Manny the angel who tells him it's time to prepare their battle plans.
John has other pressing matters to take care of, so he uses a spell and figures out the young girl killed her parents.
In order to learn more, John meets with a former client (and paralegal) who gives him all the details of the case. She leads him to Marcelo, the first victim. A chat with Marcelo might help, so John visits him at an asylum. Unfortunately, the man is no help as he's fully catatonic.
Elsewhere, the malevolent spirit leaves the girl and takes possession of a boy named Henry.
While investigating John and Chas notice that all the murders take place along the same ley line. John uses a thurible and frankincense to walk the ley line which leads the duo directly to young Henry's door. John decides to keep an eye on Henry for now.
Unfortunately, the next day at school Henry injures another boy which prompts John to confront the boy's parents. He shares the truth about who he is. Upon hearing John's wild claims the boy's father has him arrested.
Manny pays John another visit while he's locked up. The angel informs him he's there to offer guidance and has watched over him a long time.
Henry's mother eventually realizes Constantine was telling the truth about her son's possession. She bails John out of jail and they make plans for a seance. For some reason it does not work, so they return to the woman's house.
There they encounter a fully possessed Henry who John attempts to subdue. The boy escapes and heads to a nearby Halloween carnival.
Henry runs into the funhouse, but John catches up with him. He confronts the malevolent spirit and soon realizes it's catatonic Marcelo.
Constantine uses an incantation to exorcise Henry sending the spirit back to its original body. Marcelo comes to at the asylum where security guards are forced to subdue him. John managed to pull off a child exorcism, which should help his confidence.