Lost Girl follows supernatural seductress Bo, a Succubus who feeds on the sexual energy of humans. Growing up with human parents, Bo had no reason to believe she was anything other than the girl next door — until she drained her boyfriend to death in their first sexual encounter. Now she has hit the road alone and afraid.
She discovers she is one of the Fae, creatures of legend and folklore, who pass as humans while feeding off them secretly and in different ways, as they have for millennia. Relieved yet horrified to find out that she is not alone, Bo decides to take the middle path between the humans and the Fae while embarking on a personal mission to unlock the secrets of her origin.

With the help of her human sidekick, Kenzi, and Dyson, a sexy police detective, Bo takes on a challenge every week helping a Fae or human client who comes to her to solve a mystery, or to right a wrong.