"Arrow" Season 2, Episode 9, "Three Ghosts" marks the final show of Oliver Queen's Arrow in the year 2013. In Arrow 2x08, Barry Allen (Grant Gustin) plays a crucial role in an operation involving Mr Queen (Stephen Amell) and his team. This is an "unforgettable mid-season finale" according to a promo from The CW. Expect more of The Flash and a lot more impressive stunts. Scroll down to watch the sneak preview.

Spoiler alert: This feature recaps the highlights of Arrow 2x08 and brings up minor spoilers from Arrow Season 2, Episode 9, Three Ghosts.

"Tonight's episode belongs to @grantgust. You should believe the hype," announced Oliver Queen himself, Stephen Amell, on Twitter. The actor had made this shout-out a week ago, when Arrow Season 2, Episode 8, "The Scientist" first aired on The CW.

Review: Grant Gustin as Barry Allen aka The Flash (Origins) in Arrow Season 2

Some fans argued Grant Gustin was convincing as Barry Allen in Arrow Season 2, Episode 8. But there were also some criticisms against the young actor's acting chops. As Sebastian Smythe of The Dalton Academy Warblers in the FOX show "Glee," Gustin was quite all right in his "bad guy" role. As a comic superhero, however, fans are polarised in their reception of him. But when he's with Felicity Smoak (Emily Bett RIckards), sparks do fly.

In Arrow 2x08's cliffhanger ending, Felicity tells Barry Allen to save her friend. Now there's one more person who knows of Mr Queen's real identity. And he couldn't be more thrilled. The Flash, however, has yet to showcase some amazingly swift skills beyond his scientist powers.

Arrow Season 2 Spoilers: More Malcolm Merlyn (John Barrowman)

Meanwhile, it's been revealed that Moira Queen (Susanna Thompson) has connections to the League of Assassins. She is now unafraid of Malcolm Merlyn (John Barrowman), who is Thea Queen's (Willa Holland) real dad. (Tommy Merlyn, RIP, would have been both devastated and thrilled.)

Watch this online sneak peek of Arrow 2x09, showing Barry Allen, Felicity and Diggle (David Ramsey) in save the Arrow mode.

VIDEO: Watch Arrow 2x09 Promo (Spoilers)

More of Grant Gustin as Barry Allen in Arrow Season 2, Episode 9, Three Ghosts, the show's mid-season finale. It remains to be seen whether this is really the last time Arrow fans would see The Flash in the series. But The CW seems to be really liking The Flash as an independent series in the future, reports say.

Arrow Season 2, Episode 9, Three Ghosts (Arrow 2x09) airs Dec. 11 on The CW. Slade Wilson (Manu Bennett), Shado (Celina Jade), and Sara Lance, the original Black Canary (Caity Lotz) are expected to be back in Oliver Queen's mind flashbacks. So, who are the three ghosts?

More Arrow Season 2 Spoilers and TV Guide Features

'Arrow' Season 2x08: Watch 'The Scientist' as 2013 Penultimate Show; Olicity Meets The Flash aka Barry Allen [WATCH]
'NCIS' Season 11, Episode 10, 'Devils Triad' Spoilers: Gibbs is Shocked in New Episode Dec. 10 [WATCH]
'How I Met Your Mother' Season 9, Episode 13, Spoilers: 'Bass Player Wanted' to Show More Cristin Milioti? What Fans Know So Far! [READ]