Watch 'Arrow' Season 4 episode 22 live: Curtis joins Felicity and Noah's hacker team; HIVE-controlled Thea attacks Oliver

The penultimate episode of "Arrow" Season 4 will aired by the CW on Wednesday, May 18, and it will take Oliver (Stephen Amell) and his friends one step closer to stopping HIVE's plan to destroy the whole world. "Lost in the Flood" will also see Mr Terrific aka Curtis (Echo Kellum) in action after a long time.

Spoilers Ahead

In the previous episode of "Arrow" we saw Felicity seeking an unlikely ally to stop nuclear missiles from killing millions of people. Noah's (Tom Amandes) involvement in "Monument Point" did stop Darhk (Neal McDonough) from becoming infinitely more powerful than he would have been, had the father-daughter hacker duo hadn't misdirected the missile.

However, Darhk is still a lot more powerful than Oliver, and Thea (Willa Holland) is now in the underground world that he created for the people who are protected from the manmade apocalypse. Felicity can use all the help she can get to stop the big bad, and she turns to the man who helped save Ray (Brandon Routh) from Darhk once, Curtis.

Also Read: Will Cisco's vision of apocalypse come true in "The Flash" Season 2 finale? 

In the promotional photos released by the CW, he is seen in the Arrow cave, working with Felicity and Noah. This team might turn out to be Felicity's nightmare, but it sure looks like her dad is having fun, and Curtis as always, is surprised or starstruck. The photos can be viewed via comicbook.com.

Meanwhile, Oliver and Diggle (David Ramsey) will go on a rescue mission for Thea in "Lost in the Flood." From the promo for the episode, though, it looks like they might be a tad too late.

The video suggests that the HIVE has turned Thea into a loyal follower, much like Andy (Eugene Byrd). She attacks Oliver when he asks her if she is okay, even threatening him with, "Move, and I will kill you." Hopefully, she is not so far gone that Team Arrow can't bring her back.

Don't forget to watch Season 4 episode 22 of "Arrow" which airs at 8 p.m. (EST) on Wednesday, May 18 via the CW. You can also live-stream "Lost in the Flood" via CWINGO and The CW Seed.