After initially holding it off -- likely because it contained spoiler-sensitive information about the identity of Prometheus, The CW has released the official synopsis fro March 22's episode of Arrow, titled "Kapiushon."
The title appears to be a bastardization of the Russian word "Капюшон," which means "hood." That interpretation makes sense, as the flashbacks (which take place in Russia this season) are setting up Oliver as the character he was when the series started five years ago -- a character who would come to be known as "The Hood" upon his return to Star City.
You can check out the official synopsis below.
Prometheus (Josh Segarra) goes to great lengths to break Oliver (Stephen Amell). Meanwhile, in the flashbacks, Anatoly (guest star David Nykl) becomes worried about Oliver's increasingly violent tendencies, which come to a head in a brutal confrontation.
Kevin Tancharoen directed the episode written by Brian Ford Sullivan & Emilio Ortega Aldrich.
Given Anatoly's power within the Bratva, it seems plausible that it's this disagreement with Oliver that might get the archer sent back to Lian Yu, where he was found at the start of the series' pilot. Since Anatoly himself was there at one point, and rescued and sent on his way by Oliver's actions, it would be a bit of symmetry to have him strand Oliver there for his own good and/or safety.
The brutality that Anatoly takes issue with is something that Oliver and Team Arrow wrestled with mightily throughout the first two seasons of the show, and one of the consequences of that brutality was the creation of Prometheus, season five's main antagonist.
MORE: Arrow EP Says Prometheus Was Inspired By Classic Movie Villains / Prometheus's Identity Revealed on Tonight's Arrow / Is Susan Williams Working With Prometheus on Arrow? / Arrow: Even the Actor Didn't Realize He Was Playing Prometheus At First