Episode 1: "Mother's Little Helpers"
Daimon and Ana Helstrom are siblings who live in Portland and San Francisco, respectively. Daimon is a college professor who aids the Saint Teresa Center for Mental Health with cases using his demonic based abilities. At the same time, Ana works as an antique dealer who scours and kills criminals with her psychic powers. Their mother, Victoria, is held in Saint Teresa's due to her demonic possession by a demon named Mother. Her husband was a serial killer Satanist. Daimon is forced to work with Gabriella Rosetti, an agent from the Vatican, by Louise Hastings after an orderly named Keith Spivey disappears following a raid on a demonic tomb. Ana and her ally, the Caretaker, discover a strange skeleton in the tomb, and Ana takes the skull to examine. Gabriella, a skeptic, confronts Mother but has to be rescued by Daimon and Hastings. Daimon finds a symbol his Mother has drawn on the wall, and Ana finds the same symbol on the skull. The siblings reunite at Saint Teresa's. Elsewhere, a demonically possessed Spivey attacks a trucker.
Episode 2: "Viaticum"
The trucker, Alex Tilden, is taken over by a demon named Magoth and is saved by a good samaritan, only to crash their vehicle. Daimon and Ana have a bittersweet reunion as they argue over what to do with Victoria. Daimon wants to save her while Ana wants her dead. Ana has a bad meeting with Victoria when she tries to extract information from her and is scolded by Daimon for being careless. Ana's partner and cohort, Chris Yen, is left to watch the skull and becomes entranced by it. After telling Caretaker where Ana went, Yen has it bite his arm and later kills the brother of one of Ana's victims. Ana goes to speak with Victoria despite Hastings' warnings and learns that Spivey was sent, not to free the demon from its tomb, but to kill it. Victoria tells Ana she was the favorite, presumably of their father. Daimon and Gabriella get called away to deal with Magoth. Alex is slowly dying, so Daimon expels him from his body to save his soul. Magoth warns Daimon of the demon Spivey unleashed, and Alex, in his dying moments, makes peace with his wife and son.
Episode 3: "The One Who Got Away"
Victoria has become more lucid and speaks with Daimon and Ana together. Ana reveals to Daimon that their father is back from the dead to finish what he has started. The siblings and Gabriella head off to meet with Zoe Richards, a survivor of their father's killings. However, Ana deduces that she is lying, as their father left no one alive, and that someone else is in the house, but they are kicked out. Caretaker meets with Hastings, and they catch up on their friendship. Mother sends one of Saint Teresa's patients after Caretaker, but he takes him out easily. He later learns that Hastings has lung cancer and that Gabriella is set to replace her. Daimon and Gabriella go back to the house and discover that the woman they spoke to is Aubree, Zoe's twin sister. Zoe is horrifically burnt and hiding in the basement. She sets the house on fire, but they all escape. Aubree leads Ana into a trap as revenge for her involvement in harming Zoe years ago. Spivey, possessed by the father, instead devours Aubree into himself while Ana escapes with Daimon.
Episode 4: "Containment"
Daimon, Ana, Gabriella, Hastings, and Caretaker gather to discuss Daimon and Ana's father's return. Caretaker informs them that the skull can be used against him, so Daimon and Ana head to San Francisco. However, they discover the skull missing and Yen's victim dead at the scene, with Yen himself as the culprit. As they clean up the mess, Ana admits to her vigilante actions. Daimon scolds her but later helps her come to terms with her pain. A possessed Father Crow attacks Gabriella, but Caretaker rescues her, and they take his body to the Blood hideout where they keep possessed victims in comas, horrifying Gabriella. Hastings speaks with Mother, who reveals her name is Kthara, that she has "children" of her own, and that she was the one who gave Hastings her cancer. Gabriella argues with Hastings on their methods but realizes that they have no choice. Daimon and Ana return home and are attacked by Magoth, but expel him from his current host Bryce. Yen takes the skull into a hidden tunnel and slowly begins to lose his sanity.
Episode 5: "Committed"
In a flashback, Daimon calls child protective services as a delusional Victoria awaits Ana's return and is committed. Bryce approaches Daimon with what happened to him recently, and he gets Gabriella to come and consult with him on his experience. Victoria is found digging into the floor and gets placed into a coma. They realize that Yen is nearby with the Keeper's skull, and Daimon, Ana, and Caretaker venture into the tunnels underneath. They find Yen, who has lost his sanity, but the Helstroms fight with each other over what to do. They soon catch up with him and knock him out. Victoria is trapped in a nightmarish version of her house with young Daimon and Ana before Kthara reveals herself and asks for protection. Victoria quickly learns that Kthara is hiding from the Keeper and lets him take her, allowing her to awaken. Daimon and Ana converse with their mother though she is unsure if Kthara is gone while Yen is committed. Gabriella takes Daimon to the Blood Hotel to see the patients but discovers that the entire staff has been killed.
Episode 6: "Leviathan"
A possessed Spivey injures his wife Jolene. Caretaker is missing as Daimon and Gabriella head back, but must stop at a gas station after getting a flat. They are attacked by the Blood Hotel patients with Daimon having to use his demonic powers to defeat them. Meanwhile, Ana tends to a slowly recovering Yen who still craves the skull. She further reconnects with Victoria; realizing that she truly loved her and understood why she was unaware of their father's treachery. Spivey breaks into Saint Teresa's and kills one of the guards. Hastings discovers the body and puts the hospital on lockdown, but they are trapped inside with the power out. One of Spivey's possessed victims steals the skull from Victoria, but an escaped Yen kills him and retrieves it; willingly giving it to Ana after she admits that she missed her mother. Daimon and Gabriella arrive, but Spivey tries to make off with Victoria. They use the skull to incinerate Spivey. Kthara takes control of Victoria and takes Spivey's remains with Ana realizing that Spivey was not possessed by their father.
Episode 7: "Scars"
Kthara tends to Spivey's remains, who is possessed by Basara, and decides that they need a new host for him. Daimon and Ana have another argument over recent events that results in Ana taking Yen and heading back to San Francisco. Ana tries to revert to her old vigilante habits, but Yen prevents her, especially when his boyfriend Derrick arrives demanding to know why the police database is being accessed at their workplace. Ana privately tells him that she was paranoid and he forgives her. She breaks down when he nearly drains him, but Yen comforts her. Caretaker has been kidnapped by the Blood who call Daimon demanding a compromise as they do not trust the Helstrom family. Daimon is hesitant when he learns that he and Hastings decided on separating the siblings, but is encouraged by Gabriella. They arrive at the meeting place, but the Blood attack him with the same dagger that marked his chest. Daimon angrily gives in and incinerates some of the members while the rest flee. Gabriella is shocked by Daimon's demonic display.
Episode 8: "Underneath"
Daimon and Gabriella take the dagger and warn Ana who has come to help. They later leave it with Hastings and head to the old Helstrom house to retrieve the other half of the dagger. The house is currently on the market and is scouted by Blood Members, forcing Daimon and Gabriella to wait them out. Daimon leaves a trap and appears to be on the verge of killing the members in front of Blood leader Esther Smith. It turns out to be a warning and he leaves the members unharmed and retrieves the dagger piece. Ana convinces Hastings to help try to destroy Kthara with the dagger. They find her hiding place and a struggle ensues with Ana ultimately choosing to suffocate Victoria and then reviving her; finally freeing her from Kthara. Daimon hears the news from Ana and he and Gabriella become intimate. While Daimon showers, Gabriella is suddenly possessed by the spirit of Kthara; having been marked by Spivey earlier. She attacks Daimon and proceeds to have Basar take him over. Afterwards, the two of them have sex to procreate.
Episode 9: "Vessels"
Gabriella awakens in a sealed off room and learns that she is pregnant. Kthara communicates with her and reveals that she is being reborn inside of her as her pregnancy rapidly goes to full term, but Gabriella manages to escape. Basar in Daimon's body attempts to kill Victoria, but Ana stops him and Hastings and Caretaker seal him in a cell. They realize that Basar's organ was placed into Daimon's back and that in order to remove it, they need to use the dagger. Victoria talks to Basar and manages to break him down, but Hastings takes her home. Gabriella arrives, but is severely injured from her escape. Yen begins to experience the voices again, sees glyphs forming on his arm and an eyeball in his throat and tries to contact Caretaker. With no other option, Ana tries to use the broken dagger to remove Basar from Daimon, but needs the other half which the Caretaker was going to use for Gabriella's baby. As Kthara's minions arrive to retrieve Gabriella, a fully conscious Daimon attempts to perform an exorcism on himself and savagely knocks himself out.
Episode 10: "Hell Storm"
Kthara's minions stab Hastings in the back, sending her to the hospital, while Gabriella escapes and comes in contact with the Blood. Basar takes Daimon over again and escapes. He and the minions take Gabriella peacefully to their hideout. As Ana and Victoria make up, Yen comes to them and Caretaker about his condition and is informed that he is the new Keeper. Yen suddenly has the knowledge on how to fix the dagger and Ana and Victoria put the pieces together. Ana and Yen find the hideout and confront Basar and remove him from Daimon and incinerate him for good. Daimon uses the dagger to kill Raum and Magoth; freeing their vessels. Gabriella gives birth to a girl, but becomes disillusioned and decides to join the Blood. Daimon and Ana decide to raise the baby as they, Victoria, Caretaker and recovering Hastings celebrate. One month later, Yen is watching an adolescent Kthara when they are approached by a man identified as "Papa". He reminds Kthara that her name is "Lily" and takes her from Yen, while killing innocents, to Yen's horror.
