Oliver promises to help Diggle get to the truth behind what happened years ago between Dig's younger brother and Damien Darhk in this teaser for next week's episode of "Arrow."

Starring Stephen Amell, David Ramsey and Emily Bett Rickards, "Arrow" airs Wednesdays at 8 pm EST on The CW.

"Brotherhood" - Team Green Arrow's ongoing battle with Damien Darhk (Neal McDonough) is complicated by a shocking revelation. Thea's (Willa Holland) bloodlust returns and she loses control in front of Alex (guest star Parker Young). James Bamford directed the episode written by Speed Weed & Keto Shimizu (#407). Original airdate 11/18/2015