John Constantine takes a break from his usual sidekicks to team up with his drug-addled professor pal Ritchie. When a group of students at Ritchie's college accidentally connect with a dimension-hopping serial killer (played by Lost's William Mapother), it's up to the two of them to put a stop to a slasher film.
John's in a wallowing mood, but Manny interrupts his one-man pity party to send him Ritchie's way, even though John is usually the last person Ritchie wants to see. However, what Ritchie doesn't realize is that Adam, one of his grad students, just played a deadly game of Bloody Mary with a bunch of his friends.
So Ritchie, haunted by the Astra incident and finding the sedatives aren't enough to keep him from hating himself, has been looking for a cheat code for spiritual nirvana. He and Adam have been studying the works of Jacob Shaw, a particularly vile occultist, to see if his journeys across dimensions could inform digitally uploaded consciousness. One night, however, Adam uses one of Shaw's rituals not for occult science, but as a spooky game. Four kids go into a graveyard, sit on Shaw's grave, and really do enter another world. Unfortunately, it's Shaw's world, a place where he hangs around and creates phantoms in order to kill them.
Once the kiddos have entered Shaw's domain, he's able to track them in the real world, enacting his own little horror movie. He finds the students one-by-one in reflective surfaces and pulls them back into his pocket dimension murder house, killing their bodies in our world and keeping their souls so he can kill them over and over again.
We get a sort of final girl in the form of Adam's girlfriend Lily, but she's not the one who brings down the monster. No, that's what we've got John and Ritchie for. We've seen a lot of John's old gang, but they're usually working in support of John. Here, John is working in support of Ritchie, who quickly realizes that, after all of his metaphysical research, he can overwrite Shaw's world. In fact, it's Ritchie who exposes Shaw for what he really is, a sad little god of a rather uninteresting world, a man who can't think of anything better to do with his omnipotent eternity than star in his own Wes Craven film.
After Ritchie manages to destroy Shaw and his murder bungalow, sending the dead kids' souls off on their next journey, he decides he's going to carve out a bit of Nirvana for himself. He can stay in Shaw's pocket universe and hide out from the Rising Dark. But ultimately, he doesn't have the will to stay there. It makes sense, given that Manny was so intent on John giving Ritchie a hand. And it's a rather sharp moral for Ritchie in the end, Ritchie who has long blamed his suffering on John: life is full of suffering and we suffer because we crave something better. The world of Constantine is certainly full of suffering, but perhaps someday Ritchie can put his craving to something more productive than his own personal Nirvana.
However, John knows that trying to do something productive, trying to counter the Rising Dark, just leads to more suffering. He's still very much in the cycle that Ritchie wants to break out of. He ends the episode just as he began it, with a glass of whiskey and his own guilt.