Oliver must tackle a new threat to the city when bombs start to go off in Starling City. Felicity discovers the person setting them off is Mark Sheffner, a man who goes by the nickname Shrapnel. Arrow discovers Shrapnel's next target is Sebastian Blood's "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 races to the plaza to find the bomb before it goes off. Meanwhile, Roy continues to hide his new strength from Thea but, after she witnesses his super strength in action at the rally, she demands answers. Laurel's suspicions about Sebastian grow stronger once she learns that he grew up with Cyrus Gold, the man who killed Lance's partner. After Donner refuses to help her investigate, she turns to Arrow for help.
Spoilers ahead. Coverage follows the scope labeled below.
Complete story — includes the ending
Oliver continues his search for the man in the skull mask while Felicity travels to Central City to visit Barry, who is in a coma after being hit by lightning. Serial bomber Mark Scheffer, who goes by the name "Shrapnel", sets off bombs across Starling City as an anti-government movement. Blood begins his campaign for mayor and decides to organize a Unity Rally for the city. Scheffer targets the rally, but Oliver is able to stop him and get him arrested; the bombs are disarmed. During the commotion, Thea witnesses Roy using his new strength and confronts him. As the Arrow, Oliver makes an alliance with Blood. Meanwhile, Quentin starts looking for Cyrus' mole in the police department. Investigating Blood, Laurel visits a mental institution where she finds Blood's mother, who reveals that he killed his father and put her in the asylum to cover it up. In a flashback, Slade experiences adverse effects on his mind and personality from the Mirakuru, which leads to him secretly separating from Oliver and Sara.