Inside a mausoleum, several college students are having fun messing about with spells. Suddenly, they find themselves transported to different rooms in a mysterious house. To make matters worse, there's a killer lurking through the dark corridors.
The kids manage to escape, but they're now marked for death. They have unknowingly opened a very dangerous portal to an alternate realm.
Manny appears to John and tells him his friend, Ritchie, is in need of assistance. As it turns out, those kids are Ritchie's students and the spell book belonged to him.
Ritchie is not pleased to see John and is reluctant to even deal with him but John breaks the bad news that Gary is dead. He refuses to lose another friend and is determined to help whether Ritchie likes it or not.
Meanwhile, a student mysteriously dies on campus. He was killed in that other dimension, but his body died in the real world.
Lily, one of Ritchie's students that took part in the ritual, confesses that a group of them were using spells at the graveyard.
John visits the mausoleum and uses an enchantment to unveil glyphs used during the ceremony. This was a case of out body travel to alternate dimensions.
"If those kids actually made it into another realm, then they've opened gates that won't be easy to close" John warns Ritchie.
John's mate has news of his own, he explains that if you're killed in another dimension your body here suffers the same form of death.
Constantine and Ritchie take Lily, the sole survivor, to the millhouse thinking its enchantments would protect her. Sadly, all it took was the reflective surface of her mobile phone for the killer to pull her into his perverse world.
John and Ritchie decide to enter the madman's realm. Once there, Ritchie realizes he had studied enough about other planes to alter this new reality around them. He rearranges the gloomy world and let's the light in defeating the killer and saving Lily's life. Unfortunately, her friends had to stay behind because their physical bodies had already died in the real world.
For just a brief moment, Ritchie considered staying behind and making this reality his own.
John made a decent case for returning with him and living an actual life helping Ritchie to snap out of it.
This shared experience seemed to bring the two old mates closer together. I bet Ritchie is grateful John stuck around.