Bo Dennis is a succubus, a mythological creature who uses sex to feed, heal, and kill. Raised as a human by strict adoptive parents, she was taught that sex of any kind was evil. When Bo's internal need for sexual energy, or chi, became too strong at age 17; unable to control her power, she accidentally killed her first lover. Traumatized, Bo left town, vowing to never succumb to her urges again -- until she met the Fae, her ancient, long-warring kin. Fae police detective Dyson and human doctor L a u r e n helped Bo understand and feed her inborn needs, but control her appetites so that she can live a "normal" life -- sparking a love triangle. Rejecting the Fae rule that she choose between the Light and Dark Fae factions, Bo found a steadfast ally in Kenzi, a human criminal with a good heart and fierce sense of loyalty. Together with Kenzi, Bo uses her supernatural abilities to help Fae and human alike, while unraveling the continuing mystery of her origins.

Lauren Lewis is a talented human doctor who grew up very differently than Bo. Coming from an upper middle class household, she is much more cultured and graceful than the less refined B o. While working in Africa, Lauren unknowingly treated and cured a plague-ridden Fae tribe. Her girlfriend at the time, Nadia, was cursed and fell into a coma, leading the Ash to offer Lauren a job working for the Light Fae, in exchange for her being allowed to find a cure for Nadia. Lauren is regarded as the Ash's property; she works as a scientist and studies life forms, like Bo, that many humans will never know even exist. Lauren offers her medical knowledge to Bo to help control her hungers and protect her from the Fae punishments. Lauren has come to rely on Bo and seeks her out for protection against the new Ash.

My God, you're b e a u t i f u l. I know what you're doing. Do you want me to stop? No. That was some serious s p a r k a g e; I think she likes you. You are definitely c u r i o u s. I'm not so sure it's scientific. I like your necklace. This time, I was Bo's h e r o. The point is, you s a v e d us. You're getting awfully good at doing that. I don't want to hurt you. I t r u s t you. Nobody owns you. I've m i s s e d you. I owe you that last talk. You just please come back s a f e.