Back in town for her brother’s funeral, a young woman named Taylor (April Billingsley) ventures to the bad part of town so she can score some drugs to deal with her grief. However, she finds herself attacked by a hulking figure and is left comatose, riddled with blackened veins. At the safehouse, Zed (Angelica Celaya) is still healing from her episode a few weeks back, but her meditation is interrupted by a pep talk from John (Matt Ryan), who wants her to continue helping him fight the forces of evil. Manny (Harold Perrineau) appears once again to push John in the right direction, but he insists that the scrye map Constantine has been using to track the rising darkness has become a crutch–one he relieves him of by burning with angelic fire. Instead, Manny gives John a bit more direction, telling him to go to the hospital and investigate the strange case of the young woman Taylor. Poor Chas (Charles Halford) gets them in the door of the hospital with a hastily-improvised screwdriver wound in his leg, freeing John and Chas to search for Taylor. Finding her, Zed tries to use her psychic power to learn what happened to her, but only has a chance to see an angelic vision and a heavenly light before she is once again struck down by the force of her abilities. Taylor also succumbs to her supernatural wounds, the first victim of this latest threat.
While the stricken Zed is examined by a handsome young doctor named Gaelen (Nick Gehlfuss), John and Chas sneak off to the morgue to glean what they can from Taylor’s corpse. Casting a spell, John is shocked to see nothing but pure darkness emanating from her body, hinting at an older, darker magic than he’s used to dealing with. Dr. Gaelen informs Zed that she has a small tumor in her temporal lobe (the source of her powers, or a side effect of them?), and a hard-drinking orderly becomes the latest victim of the hulking attacker.
John heads to the rooftop for a smoke, where he is joined by a Dr. Carroll (Robert Pralgo), who wants one of his own. But Manny once again appears, this time in the doctor’s body, to offer the usual cryptic guidance. A frustrated John uses a vial of air from Hades to knock the angel out, then casts a spell to trap him in the doctor’s body. This time, he won’t be able to just drop hints and disappear–against his will, Manny will have to take a more active role in the case.
Back inside the hospital, John and Manny find the second victim’s body, and John goes digging around inside the poor guy’s guts for clues as to what felled him. He discovers a blackened heart, which leads Manny to conclude that the killer is powered by the Heart of Darkness, a shard of black diamond with ancient origins; summoned forth by a sorcerer centuries ago, the diamond was shattered by an angel’s sword and its pieces were spread across the world by the great flood. John returns to the safehouse to gather more information about the black diamond, while Manny, still trapped in Dr. Carroll’s body, uses the hospital computers to learn more about the victims. At his safehouse, John is in possession of his own shard of the Heart of Darkness, which he has Chas hold onto to test its effects: soon Chas is filled with rage and covered with black veins, prompting John to zap him with a cattle prod to free him of its influence. It seems that those who fall under the sway of the diamond lose themselves to their anger and have their strength increased to match, and based on the sad history of addiction the victims’ medical records reveal, the latest acolyte of the diamond is targeting people with substance abuse who have recently fallen off the wagon. All signs point to a massive, abrasive burn victim named Morris (Michael Beasley) who is hanging around the hospital awaiting a skin graft. Morris is easily big and mean enough to be the one behind the killings.
While talking about treatment options with Zed, Dr. Gaelen reveals that he did a tour of duty in Baghdad, and is himself afflicted with something dangerous lodged in his body–a piece of shrapnel near his heart. Zed is also able to see through Manny’s disguise, and once they are alone, she asks if her powers are heaven sent. As usual, Manny is less than forthcoming.
Morris goes outside for a cigarette, and is felled by the diamond-powered killer. John tries to intervene, but is knocked out. Coming to, he and Manny share their intel with one another, and conclude that Dr. Gaelen must be the killer–the shrapnel he received in Baghdad must contain a piece of the Heart of Darkness, and he is wreaking vengeance upon those who have been squandered the second chances life has given them. To this end, Zed, having decided against having her tumor removed (it might interfere with her visions, which, destructive though they might be, have helped her save lives), is the next likely victim. John uses his fragment of the diamond to track him, and he and Manny arrive in the nick of time. They are easily overpowered by the transformed doc, but Zed realizes that her visions of a heavenly light were leading her to the answer–only Manny’s heaven-sent powers can shed light on the Heart of Darkness. John reverses his spell, freeing Manny from a very surprised Dr. Carroll, and Manny enfolds Dr. Gaelen in his wings to bring him to his heavenly reward. Afterwards, as Zed prays for guidance, Manny (who she can now see) assures her of the divine origins of her abilities.
DC Comics Easter Egg Watch: The Heart of Darkness is a tool of evil utilized in the DC Comics Universe by the supernatural villain Eclipso, who is able to take possession of those who hold it. Eclipso has given just about every DC hero a hard time at one point or another, particularly in the 1992 crossover The Darkness Within, which saw all the heroes (even heavy hitters like Superman and Captain Marvel) fall under the black diamond’s influence.