The stem cells did originate from Kira's tooth, although the story of how the Dyad got a hold of it was rather boring: they obtained it from the hospital, where the girl had been recovering from the hit and run last season. Cosima learns this after she confronts Scott and Delphine about their conversation she happens to overhear and kicks her lover out of the lab for hiding the truth from her.
Alison opens up to Vic: she confesses that she slept with her best friend's husband. Oh, and then she watched her choke to death too. That feels so good to say it out loud! Shortly after she follows her new friend to his room to give him the 9-finger gloves she made just for him and hears Vic speaking on the phone with Angie, whom he promices dirt on Mrs. Hendrix! Ally calls Felix, who comes to the rehab next morning, and together they face the traitor.
In exchange for his silence, Vic demands to see Sarah, and when his ex appears, he announces that he wants her back in his life. The speech he gives wasn't meant to be finished, as Fee has spiked his tea, so the guy loses conscience and falls with his face down to the table, and gets covered in all the glitter that Alison used to decorate the nametags for the family day.
Long story short, Angie finds her informant blacked out under reception desk, Sarah impersonates Alison for a while, and all that. Finally, Donnie walks in on both Sarah and his wife together in one room. Expecting that he knows the whole story, Ally announces that Sarah is her clone. However, it turns out that even though Donnie is indeed her monitor, he's been kept blindfolded. Leekie hired him to conduct "a social-metrics study" (I can't believe he would't tell her that, when she tortured him last season, but whatever). Alison says that he ruined their family with all the spying and lying.
Mrs. S visits Leekie and discovers that Rachel doesn't know the truth about her parents, so she arranges for the bitchy clone to see her dad. After that, Ms Duncan colludes with the freshly introduced evil character - someone above her in the corporation named Marian - to get rid of Leekie. She lets him hear Marian asking whether he was already killed or not, making him realize the game is over, but instead of finishing him she lets him run.
|Making evil corporate bosses female is growing old.|
Donnie finds Leekie in the street and, pointing a gun at him, demands the scientist to get in his car. He complaints about Leekie's institute probing his wife and ruining his family, and in the process, yelling "I quit" he hits the wheel with the gun, which, of course gets discharged, and there goes the great brain of Aldous Leekie - covering Donnie's car windows. Oh well.