Thea (Willa Holland) loses control of her bloodlust in the upcoming episode of the hit The CW series "Arrow."

In "Brotherhood," Comicbook reports that the effect of the Lazarus Pit will once again be felt by Thea. Worse, the urge to kill starts to consume her in front of Alex (guest star Parker Young). It seems that there is really no getting away from the darkness for those who were resurrected from the grave. Last episode, Sara's (Caity Lotz) thirst for blood returned during Team Arrow's operation to save Ray (Brandon Routh). The billionaire superhero did not die in the explosion, but was held hostage by Damien (Neal McDonough) all along.

Everyone thought that Sara was fine after Oliver's (Stephen Amell) friend Constantine (Matt Ryan) helped get her soul back. But when they had to steal an important component needed to create Ray's A.T.O.M. suit from a rival company, Sara almost killed the guard protecting the building. Luckily, the team was able to stop her on time. Her urge to kill once again kicked in while facing a H.I.V.E goon. This time though, she broke his neck before Oliver could do anything. Sara was horrified about what she has done and wanted some time off from Team Arrow.

This time, though, it appears that it is Thea's turn to be overcome by the darkness. The fact that she will lose control in front of Alex, whom she is steadily getting close to, makes it worse. Will Thea hurt Alex? Will Team Arrow lose another key member because of the Lazarus Pit? Meanwhile, also in episode 7, the group will learn of a shocking secret that will complicate matters in their quest to defeat Damien. They narrowly escaped the powerful villain last time when they rescued Ray from his grasp. Will this information give Damien more advantage on their next fight?

"Arrow" airs Wednesdays at 8 p.m. EST on The CW.