It's titled "Draw Back Your Bow" and, in addition to being the first appearance of Captain Boomerang, the episode will feature (and apparently in a pretty big way) Cupid, played by Supernatural's Amy Gumenick. Cupid, an obsessed fan of the Arrow, will debut in the sixth episode of the season while Boomerang, an irate ex-A.R.G.U.S. employee, will be introduced in the seventh episode of the season and then carry over into the eighth episode, in which he'll likely face The Flash, who crosses over into Starling City.
"Draw Back Your Bow" will be directed by "Blast Radius" helmer Rob Hardy, marking his second foray into the Arrowverse. Hardy has also directed episodes of Criminal Minds, Bones and The Vampire Diaries.