This article contains spoilers for The Flash season 4, episode 22, 'Think Fast'.
The penultimate episode of The Flash opened with John Diggle (David Ramsey) arriving at the ARGUS facility called The Castle, where Fallout (Ryan Alexander McDonald) is being kept. Digg has to go through a DNA test to prove he's good and then has them drop the power dampener because of the chip in his right arm. Once down, he switches back to Clifford DeVoe (Neil Sandilands) and starts taking out guards. It's a really cool-looking scene of him using all of his different powers from getting into people's head, to blasting sound waves or shrinking someone and then stepping on them. Each power has a different color associated with it.
One of the employees was reading Iris's blog and sends a message the DeVoe is there. When Iris (Candice Patton) gets the message, Barry (Grant Gustin) races to Star City, grabs Diggle, and brings him back. Cisco (Carlos Valdes) has a bucket waiting, and Caitlin (Danielle Panabaker) has a bottle of water. And of course he throws up. He then tells the team where Fallout is and checks the status, only to find it's too late and that Fallout is already building up energy. The team has 12 hours to figure out how to stop DeVoe before the Enlightenment happens.
Looking at the situation, there are six ARGUS employees being held over electrical plates — if the Flash runs into any, they will trigger and kill them all. But if he triggers all of them and pulls the electricity into himself, he could be fast enough to follow DeVoe through his portal. But it would kill the hostages. So Cisco comes up with the idea that he and Caitlin should go with Barry in "Flash Time" so they can save the hostages while Barry goes after DeVoe.
Meanwhile, Iris and Harry (Tom Cavanagh) try to find where Marlize (Kim Engelbrecht) could be hiding, but they differ on whether they should toss her into the pipeline and throw away the key or use her to stop her husband. And Cecil (Danielle Nicolet) has a new power as she takes on the mind of someone around her, which adds to the stress Joe (Jesse L. Martin) is already dealing with as the baby is due. Oh, and Caitlin goes to the team's therapist, who suggests she may be repressing memories.
Cisco and Caitlin aren't taking to working in Flash Time well. The ice gun won't work, Vibe can only open a baby portal, and they keep losing focus. At one point Caitlin flies out of Flash Time and hits her head, jarring one of those repressed memories. Barry balks at using them and possibly getting them killed, but Cisco lays it out that they all feel responsible and that it's not up to him to save the world by himself.
The moment comes and the team races to the Castle and go in using Flash Time. They're able to save the hostages and Barry follows DeVoe through his portal, where he has used his gravity powers to raise the satellites. But Barry races up after one of them and uses Amunet Black's grenade to destroy it. He then exchanges Friedrich Nietzsche quotes before DeVoe vanishes. Caitlin has Cisco vibe her into that repressed memory, and we see that after she got hurt in a bike accident, she became Killer Frost as a child. That means the Dark Matter didn't do anything to Caitlin that wasn't already there. And in England, Iris and Harry find Marlize and try to convince her to help them stop DeVoe.
The episode ends with DeVoe appearing inside S.T.A.R. Labs in Wells's secret chamber and using Gideon to replace the destroyed satellite with the S.T.A.R. Labs satellite, making it possible for him to do his enlightenment… and he sets it to begin.
The Thinker using all the powers he's collected was a really nice opening. The Diggle cameo was fun, and there was a nice little Easter egg as Barry mentions Black Hawk Island as a place DeVoe might launch his satellites from. I thought the Killer Frost storyline was a bit too convenient — her just happening to tap into that repressed memory after falling. And I can't say the explanation of why Cisco and Caitlin needed to go into the ARGUS facility with Barry matched what they actually did in the facility. This season feels like it's gone on a bit too long, as the team has had one failure after another and no solid victories. It's definitely time to wrap this up, tell us who Mystery Girl is, and set up the big bad for season 5.
The trailer for next week gives away how were going to have the Inception-like season finale that executive producers have been promising. Barry uses the Thinker's chair to go into his mind and battle him there, which also explains how Ralph Dibny (Hartley Sawyer) is able to help him. And since Ralph is still alive in DeVoe's brain, maybe Barry can find a way to bring Ralph back. The Elongated Man was one of the highlights of season 4, and I'd like to see more of him in season 5.