Full story
Daimon and Ana Helstrom are the children of a serial killer who scarred their childhood with blood. They grew up apart. Daimon is an ethics professor in Portland who uses demonic powers, like glowing eyes and burning hands, to help with possession cases. Ana lives in San Francisco, runs an auction house with her friend Chris Yen and secretly hunts criminals. Their mother, Victoria, has spent years locked up at St. Teresa's hospital, run by Dr. Louise Hastings. Victoria isn't just ill: inside her lives Kthara, an ancient demon who calls herself Mother.
A strange case at the hospital puts Daimon together with Gabriella Rosetti, an agent sent by the Vatican, and the Caretaker, a man who guards occult objects. Soon the siblings reunite and fight over the same old thing: Daimon wants to save their mother, while Ana would rather destroy the demon by any means. Clues point to their father coming back from the dead, and they face possessions, a trucker taken over by the demon Magoth and a house with a fake survivor of their father's crimes. A mysterious skull goes missing, and Chris Yen starts losing his mind because of it. At the hospital, a possessed patient sparks a riot, and the siblings learn their father wasn't behind it.
Mother reveals she caused Hastings's cancer and that she has children waiting for her. A group called the Blood, which hunts the Helstrom family, kidnaps the Caretaker. Daimon recovers both halves of a dagger tied to the family's past. Ana tries to kill Mother and fails. So she makes an extreme call: she smothers Victoria to death and revives her, breaking the possession. But Kthara jumps into Gabriella, who seduces Daimon.
Gabriella wakes up pregnant, and the demons speed up the pregnancy so Mother can be reborn. At the same time, the demon Basar takes over Daimon's body. Chris Yen learns he's the new Keeper. With help from Victoria, now free and clear-headed, Ana and Chris repair the dagger, pull Basar out of Daimon and burn the demon. Daimon uses the blade to free other victims.
Gabriella gives birth to a girl, Mother reborn, and loses her faith. Disillusioned, she joins the Blood. Hastings survives an attack, and the Helstroms celebrate together over dinner. A month later, while Chris Yen is watching the girl, already a teenager, a man called Papa shows up, reminds her that her name is Lily and takes her away. The show was canceled after this single season, and the cliffhanger was never resolved.