Quinn passes his test, and he and Jamie have apparently reconciled again, but when they're out at Batista's restaurant celebrating, they overhear the patrolman who brought Deb in engaging in some disparaging gossip about her, which pulls Quinn into a fistfight. Jamie's actually not upset about that one, which speaks well of her, but Quinn's situation goes south when Matthews strongly urges Batista to consider Angie for sergeant instead of Quinn. This doesn't even get resolved this episode, so zzzzz.

Dexter has crossed off three more potential suspects from Vogel's book, and as such is now up to an "A.J. Yates," a violent criminal from an early age who's now a seemingly normal cable guy – but also bears a scar that indicates he may have had brain surgery right in the area from which The Brain Surgeon has been harvesting his trophies. Suspicious of Vogel's methods, he confronts her, and Vogel admits that Yates had a lesion on his brain she guessed was contributing to his violent tendencies, so she recommended it be removed, although she never knew for sure that her prescription even came to pass.

Dexter checks out Yates' place and finds a closet full of women's shoes, individual ones at that – unaware that Yates is in the house, watching him from a secret surveillance room in which he's holding a helpless woman captive. Yates sneaks up on him, but pauses to listen when Dexter calls Vogel on speaker to report his findings, mentioning his son in the process, whereupon Yates lets him go, possibly planning to use him to get to Vogel. When Dexter returns to the house, he realizes Yates saw him and makes him as The Brain Surgeon – and also finds one of Yates' victims he thought was dead but in fact survived his stab wound.

After taking her to the hospital, Dexter grabs Vogel and returns to Yates' house – and, on his computer, discovers Yates hacked into Vogel's patient files, which contain her cold and clinical assessments of Dexter's interactions with her. Feeling dangerously betrayed, he accuses her of making him his lab rat and informs her she'll be out of his life as soon as Yates is dead. As Dexter himself notes, though, it's not clear how the girls and the shoes fit into the Brain Surgeon MO, so even if there weren't eight episodes to go it'd seem likely enough there's more going on here.

Deb, tormented by flashbacks to LaGuerta's last moments in which she sees herself shooting Dexter instead of LaGuerta, consents to visiting the scene of the crime with Vogel, and Vogel proves her acumen by getting Deb at least to admit her feelings. With Deb now staying with Vogel, Vogel also shows Deb some of the tapes of her sessions with Harry in aid of making Deb see that Harry protected Dexter in the same way she did. Returning to the shipping container, Vogel closes them in and throws Deb's crimes in her face to make her realize she'd kill LaGuerta to protect Dexter again if faced with the same choice. Deb, finally seeing the light, asks how to make it right, so Vogel counsels her to realize she made the best of an impossible situation.

Later, though, Deb sneaks a look at another of Vogel's recordings showing Harry's remorse over Dexter becoming a killer and wonders how, if Harry couldn't bear Dexter's crimes, she's supposed to live with her own. Eventually, Dexter and Deb mutually reconnect for a car ride – only Deb asks if Harry committed suicide because of what Dexter had become, and Dexter is forced to admit that he did. Deb then goes through with her plan by grabbing the wheel and steering them off a bridge into a lake, planning to kill them both. When a nearby witness saves her, though, Deb reconsiders and yanks her unconscious brother back to the surface, and although he'll survive by definition, at least at this point, it'll be very interesting to see where this will lead.