This week, Arrow welcomes back an old friend.

E! News has your exclusive first look at "Prochnost," which sends Oliver and company to Moscow but also sends Diggle on a mission to track down Roy Harper (Colton Haynes)...or should we say Jason?

He's now working as a mechanic, lying low, trying to keep his Lazarus Pit side effects at bay, until Diggle arrives asking for help. Roy's not so ready to help, though.

"Whatever you're about to ask me to do, I can't, I'm sorry," he says, reminding Diggle that he's no hero anymore because of what his bloodlust has done to him.