The first season of Arrow was about the Undertaking and Malcolm Merlyn (John Barrowman). His motivation for wanting to destroy the Glades was the murder of his wife Rebecca. He felt the best way to deal with the crime riddled area of the city was to flatten it and start over. In the clip here we see that Felicity (Emily Bett Rickards) is running a match on the gun used to kill the Alderman the previous week and the computer matches it to a homicide in the Glades two decades prior… Rebecca Merlyn.
And with having the Arrowcave bugged, Malcolm now knows that his wife's killer is Danny "Brick" Brickwell (Vinnie Jones). Which explains why the Dark Archer is suddenly back in action. Looks like Uprising is going to be a fun episode.
Arrow airs Wednesday at 8 PM on the CW.