The series opens on John Constantine being held in the Ravenscar lunatic asylum, undergoing electroshock therapy.
In both his demeanor and the narration over the scene, it's made clear that he's there voluntarily; he says that he's an exorcist, and in his line of work there are some days you just need to forget -- and some you never will.
It cuts to Constantine talking to the director of the facility, a skeptic named Dr. Roger Huntoon who asks Constantine about the murder of a young girl that he witnessed. Constantine tells him that the killer was a demon, and Huntoon says that the demon is a rationalization Constantine is using because he was unable to prevent her murder -- that we're all powerless against demons. After some banter back and forth, Constantine tells him that he can handle the girl's death, but her damnation to hell is what's eating him alive. He tells Huntoon that Constantine is paying him to make him believe there's no demons, not just to keep saying it.
Cut to a support group meeting, where a man with obsessive-compulsive tendencies is boring Constantine almost out of his seat; John sees a number of cockroaches in the hallway and gets up to follow them as they all move to a large area in the back of the facility where easels are set up to paint. There's a woman painting something on the wall -- which is covered in cockroaches -- and when he comes to try and convince her to leave it, he sees that she's possessed. His first instinct is to leave, but instead he excorcises her, with the demon doing some serious damage to the room along the way, blowing art supplies all over the room and shattering a number of giant windows overhead. Finally, the woman comes to with no memory of what happened. The cockroaches clear, and the message "Liv die" has been painted on the wall. Constantine says it means he's been wasting his time here, and that he has work to do.
Now cut to Liv Abberdine, who works at a car rental place and is dissatisfied in her job. She's talking with a co-worker before she closes up for the night and notices that the message on her fortune cookie is blank. She locks up, turns on the security system and after she walks away, the "System armed" message turns red and becomes a strange series of characters. She gets into her car, and the reverse camera in the vehicle detects an object behind her even though there doesn't appear to be one, so she gets out to check the camera and while she's doing so, the car's motor revs, scaring her. She gets into the front seat and the car won't turn on -- and everywhere she goes, all of the lights in the area turn off as well.
The ground starts to crack and open up around her, and as she scrambles away a giant fireball explodes from the resulting sinkhole. A taxicab pulls up and Constantine gets out, offering her help. She doesn't believe him, but he leaves his card with her. She leaves in a hurry, while he investigates the fiery sinkhole. Inside, he's met by an angel called Manny, who comes to warn Constantine that something bad is coming. Before he offers any useful details, though, he flies away as the authorities show up.
Later, we see that a neighbor picked up Liv and drove her home. The two go inside and to their respective apartments. Liv sees a man in the shadows walking down the hallway and hurries into her apartment; after she's safely inside, we see the shadowy figure draw a knife and stand outside her door with the blade touching the wood.
Inside, she opens her fortune cookie to see that it tells her to "trust him," while outside, the lights begin to flicker as something stalks the hallways of her apartment complex. It reaches her door, sees a glyph carved into it that glows, growls and backs away, seeing a line of salt around the entrance to Liv's apartment. Undaunted, it makes its way into the apartment of Talia, the neighbor who gave Liv the ride. We see a lightbulb pop in her apartment, and then the image on her laptop is taken over by a large, groteque-looking eye, then the scene cuts.
The next thing onscreen is a helicopter shining a spotlight, apparently directly into Liv's apartment. It startles her awake and she walks out into the hallway to see police everywhere, and that Talia is dead. She turns to go back into her apartment and notices the talismans on and around her door.
She closes herself back in her apartment and watches the coroner cart the body away. When the ambulance passes under an overpass, he starts to hear noises in the back and pulls over to check on the body. Once he opens the door, she's still again despite having just been thrashing around before he looked. He checks to be certain the body and cart are both secure, and she starts moving again. He says that he's going to get her out, and it the camera cuts away as everything goes dark. When we can see again, she's looking very...zombie-like, and all we hear are his screams.
The next morning, a police officer takes Liv to work, where Constantine is waiting. She tells him about Talia, and he tells her he's sorry to hear about it; she shows him the sigil from her door (a photo on her phone), and he identifies it as the Eye of Horus. He says it's a protective sigil. She tells Constantine that she'd seen a man in her hallway, and thought he was Talia's killer. Constantine pounds on the cab roof and Chas exits briefly to greet her, Constantine telling her that he had actually been the one to leave the protection on her home.
He tells her that they need to get her somewhere safe, lest bodies keep piling up. He tells her that he knew her father -- Jasper Winters -- and that he promised that he would look after her. She says that her father died before she was born, but Constantine tells her that he died just last year -- that he was a good man. He gives her a small bag that he says belonged to her father, and that he wanted her to have. As she does, the medical examiner's van speeds through the parking lot, slamming through the front of her work and crushing her desk inside. When Constantine and Chas go clear the office, the possessed Talia is still on the hood of the van, having crashed through the windshield. He asks who she is and who sent her, and the "Endeavor Car Rental" sign explodes, briefly illuminating "Devil" as it does so.
Liv has taken off during the confusion, headed home to her mother to ask about her father. Her mother doesn't want to talk about it, but Liv is insistent. She opens the small bag Constantine gave her and produces a medallion, asking whether her mother has ever seen it, saying that it belonged to her father. As she does so, she sees a pale, old woman brushing her mother's hair. She exclaims that it's her grandmother, and as she does so, the old woman's face melts into a ghastly, bloody mass and she shrieks.
She runs out, her mom shouting after her, and drives away -- then sees Constantine standing on the side of the road and pulls over. She asks him what's going on and he says that she can use the pendant to see the world the way it really is. He has her hold it, and she can see a dark sky with roiling clouds and a number of ghostly figures that Constantine says are trapped souls. He can't see them but he knows they're there. he asks what else she sees, adn she says there's a train coming. He stands on the tracks, holding her hands and holding her in place. She struggles and panics but ultimately the train passes through them. Constantine laughs.
She asks why she can see things, and he says that she has her father's gift -- that there are parallel planes of existence. He tells her to park her car at her mom's and come with them in the taxi. Chas drives them, and she asks him how her father died. He says "bravely," and Constantine says he doesn't want to talk about it, only to save Liv and square his debt with Jasper. The radio is loud, it's bothering him, and he asks Chas to turn it down, but Chas can't. While he's distracted by it, they're hit broadside by a semi truck and knocked off the road. John is thrown from the car and hallucinates Astra being dragged into hell by a demon. he heads back toward the car, rescuing Liv, but an electrical cable possessed by an evil spirit bursts through Chas' chest as the three try to make their escape.
Constantine walks Liv to a stone cottage in the middle of the woods, which he said belonged to her father and where he promised to bring her if something bad ever happened. He told her that Jasper used the place for divination. Among the artifacts in the building is the helmet of Doctor Fate, which she picks up and Constantine tells her to put down. He opens an old book, and figures out that the demon chasing her is called Furcifer. She finds a map and is looking at it when her hand starts to bleed over the amulet; Constantine tells her to let the blood drop, and it points them in the direction of a place where something bad will happen. He says they can stop the demon, but that they'll have to use Liv as bait.
Outside, he's driving a truck up to a security gate when the guard stops him -- and is replaced promptly by Manny. The two talk about the situation -- Manny wants to know what the demon wants; when Constantine asks him why he should help the angels, Manny says Constantine may be able to redeem himself and save his soul from Hell. During this conversation, Manny has frozen time. He vanishes, and time resumes.
Constantine enters the office of Ritchie Simpson, asking him what's going on. An angel, he sid, told him that something's coming. Ritchie tells him that he's seen a lot of things crawling out of the shadows. Constantine asks if he can hack a power grid. Ritchie says he can, but that he won't. He says that Newcastle was a nightmare, and that he can't make it through a day without medication to help him cope. Constantine threatens to tell the police that Ritchie is the man who killed Astra. Ritchie tells Constantine that he wishes Nergal had taken him instead, and Constantine says that makes two of them.
At her father's cottage, Liv sees a spirit just before Constantine arrives; it was her father, who was being reflected in a magic mirror. He hands her a bag, and tells her it's a change of clothes. She asks how he got into her apartment, and Chas shows up, telling her that he's fine -- he has "survival skills." They prepare to make dinner before Constantine takes her to a building where he bribes the security guard to let them "have sex" on the roof. He hands the man a lightbulb and asks him to call if it lights up.
When it does, though, he's playing a video game and misses it. When the room goes black, the only things illuminated are the lightbulb and some runes on the guard's face.
On the rooftop, Constantine admits to Liv that his mother died in childbirth and he got into magic to try and talk to her spirit; his father was vile and abusive to him, blaming him for his mother's death. As they're talking about this, all the lights in the area go off, and the guard comes to the roof; Constantine quickly realizes he's not himself.
Constantine tells the demon to come get Liv, but the rune he's painted around her on the roof capture it when it tries, the guard's body melting away to reveal a dark reflection of Constantine. The reflection tells him that everyone who stands by his side dies, providing them with a fresh supply of souls. He uses another electrical cable to try and attack Liv, saying that in a city at night, with so much power running, he's God. Constantine fires a flare gun into the air and Ritchie shuts down the city's power grid. They light a fire around the sigil on the roof, trapping the demon. He brings a vision of Astra to the roof, saying that if Constantine releases him, he'll free Astra. Constantine tells Liv he's sorry, and starts casting a spell to free the demon -- but Liv touches the amulet and tells him it isn't Astra. Constantine tells the demon that he's coming for Astra, and for Nergal, and that he can pass that along in Hell. He sends the demon back, with a giant, fiery climax to ihis incantation, and then collapses on the roof. Liv asks if he's okay and Constantine says only that Ritchie will drive her home, and to go.
On the way home, Ritchie tells Liv that John is dangerous -- that he would stay away from her. He tells her that when a demon tried to take Astra, Constantine summoned Nergal to punish the demon, and instead, Nergal took both the demon and Astra, after mangling Astra in front of them. As they're headed home, Liv has Ritchie stop at Edgewood Avenue -- the location where she had foreseen trouble coming on the map earlier. There are police and ambulances al over, and a crying woman whose son had been killed.
At a bar, Constantine is debating with a bartender about the most important punk band. Chas arrives with the amulet, telling him that she's headed off to California to see a cousin and isn't coming back. She's scried a number of locations on a map of the country where she sees supernatural badness coming up, and Chas tells Constantine that they should go to them, to give Astra's loss some meaning.
Manny arrives, telling Constantine that he scared Liv away on purpose -- that Ritchie had to go out of his way to see Edgewood Avenue. John tells him that she had the right to know -- and that he will work with the angels -- but that they're going to owe him.
On the way home, a group of men with guns surround him, but he scares them away with magical fire. He's monologing about how he walks alone, because who would be crazy enough to walk with him? -- but we see the answer quickly, as a woman -- Zed -- is scawling dozens of drawings of Constantine all over her apartment.