Blast Radius

"Blast Radius" is the tenth episode of the second season of Arrow, and the thirty-third episode overall. It aired on January 15, 2014.

Synopsis
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 Scheffer, a man who goes by the nickname Shrapnel. The 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. The 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 Quentin's partner. After Donner refuses to help her investigate, she turns to The Arrow for help.

Trivia

 * After the second bombing, when Officer Quentin Lance radios in, he gives his call-sign as "DC52"&mdash;an apparent reference to DC Comics' New 52 comics universe.
 * The hospital where Sebastian Blood's mother, Maya Resik, is living, is named St. Walker's Hospital, a reference to the DC Comics character, Saint Walker.
 * This is the first time Adam Donner has appeared who was last seen in State v. Queen and seems to have fully recovered from his Vertigo overdose.
 * This episode revealed that Sebastian and Cyrus Gold had known each other years before the events of State v. Queen.

Production
Preparation ran from October 11 until October 22, 2013. Shooting ran from October 23 until November 1, 2013.