ARROW HUNTS DOWN SHRAPNEL: Oliver must tackle a new threat to the city when bombs start to go off in Starling City. Felicity (Emily Bett Rickards) discovers the person setting them off is Mark Sheffner (Guest Star Sean Maher), a man who goes by the nickname Shrapnel. Arrow discovers Shrapnel’s next target is Sebastian Blood’s (Guest Star Kevin Alejandro) “Unity Rally” and tries to talk the alderman out of hosting it, but he refuses. Arrow sets off to stop the bombing, but Shrapnel tricks him and traps him in a bomb laced antique store where he is unable to move without setting off the device. While Felicity helps Oliver, Diggle (David Ramsey) races to the plaza to find the bomb before it goes off. Meanwhile, Roy (Colton Haynes) continues to hide his new strength from Thea (Willa Holland) b