Gossip Girl - Michelle Trachtenberg

Michelle Trachtenberg will once again be pulling double duty, as she returns for the season finale of Gossip Girl, TVGuide.com has confirmed. And a Gossip Girl cast member is making his way to Trachtenberg's Mercy.

Watch full episodes of Mercy in our Online Video Guide

Connor Paolo, who plays Eric van der Woodsen on the CW's Gossip Girl, is guest-starring in the March 3 episode of NBC's Mercy, which is being filmed this week, an NBC publicist confirms.

Paolo, 19, will portray someone who sets off a pipe bomb on a bus. When he's admitted to Mercy Hospital, he's in a different kind of danger when the father of a bus passenger pulls a gun on him.