Feeding offof Lauren, alone, is leaving Bo weak with hunger, but she finds a way to ignore her ever-growing appetite when Dyson offers her a gig going undercover as a therapist at a holistic healing center. Many of the center's patients have been dying in dramatic and colorful ways, such as the man who tried to fulfill his childhood dream of tightrope walking - with no training. Dyson and Tamsin think there could be Fae at work, but since they can't access the patients' files, they get Bo to do some snooping.
Lauren is also exhausted, for the opposite reason to her girlfriend, and when Lauren finds out Bo is impersonating a doctor, the tension between them comes to a head and they have a terrible fight. They later make up, but they both realize something has changed. Bo doesn't have time to dwell on it, because one of the clinic's patients is at risk, and when Bo arrives on the scene just in time to save him, she finds the clinic's receptionist, a suicide Fae called an ixtap, nearby. The ixtap insists her powers don't kill people and that there's something else at work, then disappears.
Dyson, meanwhile, has noticed how weak Bo is, and when a bruise on her hip worsens to internal bleeding, he insists that she feed off of him. With his false promise of "no feelings involved" (note: Bo still doesn't realize he has his feelings for her back, thanks to Kenzi), she is too weak to resist, and she heals herself with Dyson's body.
Dyson then goes undercover as a patient with the regression therapist, Dr. Palmer, and when he emerges from hypnosis, he has a new aura to him that flusters all those around him. He insists Palmer isn't the one they're looking for, but Trick believes the Fae to blame is a rakshasa, a shape-shifting Fae, who could easily be disguising himself as a doctor. Dyson heads to the clinic to follow up, and when he doesn't return for hours, Bo and Tamsin take a more aggressive approach. They hold Palmer at knife point and learn many interesting things, like the fact that Palmer isn't actually a doctor, that his cat often slips onto the roof with patients, and that Dyson is up there now with the intention to prove himself a griffin.
Bo goes to talk Dyson off the ledge while Tamsin goes after the rakshasa disguised as a cat. One slash of a leaden blade and the rakshasa is history, but Dyson's demons are not so easy. Bo appeals to him through the love they all have for him, and heals the rakshasa scratch on his neck with a rejuvenating succubus kiss. She knows she has to tell Lauren about this, and her earlier encounter with Dyson, and though it's hard for the doctor to hear, they agree that Bo must feed off of other Fae if she's going to survive. Lauren has just one stipulation - no Dyson.
Bo has been so hungry that she hasn't had time to hear the pleas of Kenzi, who doesn't know who to turn to about the malignant rash on her arm, caught when she clotheslined the Norn and got Dyson's love back (last season!). Hale is similarly ignoring Kenzi after her brash interruption cost him the grace of a very important elder, and now, dejected and scared, Kenzi walks out of the Dal alone, only to be dragged violently into the shadows by an unseen force.
Tamsin tries to do the job she's assigned to do, but Bo has a hold on her stronger than The Wanderer.
Hale slips Kenzi a sacred charm that will keep her safe in the trouble to come, and tells her something that will change their relationship forever.