The final season of Showtime's popular crime drama "Dexter" is well underway, with the season's third episode coming up. Until now, fans have been plunged into the chaotic life of Dexter (Michael C. Hall) and his sister Deb (Jennifer Carpenter) after she discovers that he is a serial killer. The truth forces her to kill fellow detective Maria LaGuerta (Lauren Velez), sending her into a downward spiral.

The season's first two episodes have shown just how bad things have gotten between Dexter and Deb. Not only is their relationship on the rocks, but Deb's life in general isn't doing too well. As if Dexter didn't have enough going on in his life, someone from his past is back in his life. Dr. Vogel (guest star Charlotte Rampling) is an expert on serial murderers and also happens to be behind the code Dexter lives by.

The upcoming episode, entitled "What's Eating Dexter Morgan?," will see Dexter continue his search for the Brain Surgeon. Meanwhile Showtime teases, "Dr. Vogel tries to prove to Dexter that he's perfect as a psychopath. Debra's PTSD kicks in and she makes a desperate plea to confess to LaGuerta's murder."

In a previous interview with TVLine, executive producer Sara Colleton explained some of Dr. Vogel's motives in coming back to Dexter's life. "She has come back into Dexter's life because she needs his help, and she is highly seductive because she's trained on how to work with someone like Dexter. Plus, she knows he's extremely vulnerable at this point, so she's able to manipulate him."

A sneak peak clip into the season's third episode shows just how manipulative Vogel can be. Fans can see Vogel and Dexter talking when she asks him why he hasn't killed Deb since she found out his secret. As Vogel states Deb is now a liability but will that get Dexter to kill her?

"Dexter" S8E3, "What's Eating Dexter Morgan?," airs on Sunday at 9 p.m. on Showtime.