'Chicago P.D.' Sneak Peek: Upton Brings Back an Old Identity to Take Down a Ghost From Her Past (Exclusive)

ET exclusively debuts a sneak peek from Wednesday's episode.

Skeletons never truly stay buried.

On Wednesday's episode of Chicago P.D., titled "Ghosts," Detective Hailey Upton (Tracy Spiridakos) dusts off an old undercover identity when a ghost from her past comes roaring back into her life, and only ET has the exclusive sneak peek of the dangerous reunion between two former acquaintances.

In the clip, Upton meets her old contact, Ronald Booth (guest star Titus Welliver), a big-time meth dealer recently released from prison, as she attempts to slink back into his inner circle for her latest mission to take him and his crew down. The same dealer who killed her former partner, by the way.

"Look, I'm ready to get back in the game. We could help each other out, you and me," Upton, assuming her old cover from her previous undercover case, gamely tells Booth.

"I don't know," Booth says, suspicious of Upton's true intentions. "There's something about you."

"I'm not that mysterious, man. Just looking out for No. 1. No one else is," Upton, playing into her old undercover identity, says persuasively. Her acting job seems to have done the trick, as Booth agrees to give her another shot -- but only if she can pass one small test first. Watch the exclusive sneak peek above to see what happens next.

Before season five of Chicago P.D. officially kicked off last September, Spiridakos praised her castmates for welcoming her into the crew as the show's newest series regular. "When I first came in, I got kind of quiet and shy, so I just sat in my little corner. But they're all so amazing. I kind of stepped in and they just took me under their wing," the actress told ET on set.

Chicago P.D. airs Wednesdays at 10 p.m. ET/PT on NBC.