A villain from the past will make a return visit during this week's all-new episode of "Arrow," Wednesday on The CW.

In the upcoming episode, which is called "State v. Queen," Oliver is concerned when a mysterious illness sweeps the city, infecting hundreds of people, including Diggle. After Oliver discovers Vertigo in Diggle's blood, he realizes that The Count, played by guest star Seth Gabel from "Fringe," has escaped from prison and is once again distributing his drug, according to ScreenCrush.com.

In the meantime, the Queen family fights an uphill battle as Moira's trial finally arrives, placing the threat of the death penalty on the table. Plus, one of the promotional photos reveals that Oliver will have to rescue prosecuting DA Adam Donner from Count. It also appears that "Hot Paul" ("Orphan Black's" Dylan Bruce) gets himself into some danger.

Because of Diggle's vendetta against Deadshot, he travels to Russia, with Oliver and Felicity providing backup. However, Isabel Rochev doesn't let her partner at Queen Consolidated jet off on a business trip without her. Summer Glau revealed to TVLine more about her character Isabel and her suspicions about Oliver and Felicity and how they may move from the boardroom to the bedroom.

She told TV Line that there are definitely going to be some new dimensions to Isabel.

When asked why do she and Oliver lock horns this time around, Gau said, "She's been trying to assert her place in the company, and he's gone and scheduled this supposed business trip to Russia - but she absolutely cannot let him go without her. So they get to Russia and since they're not in the office, there's more opportunity for them to get to know each others' personality. Maybe things get revealed that otherwise would never have a chance to surface?"

"Arrow" S2E7, "State v. Queen," airs Wednesday, Nov. 20 at 8 p.m. on The CW.