As The Flash/Barry Allen (Grant Gustin) once again faces off against his greatest enemy, Eobard Thawne/The Reverse Flash (Tom Cavanagh), we get an episode filled with flashbacks, swashbuckling adventure, and. . . superhero fitbits? It all works, even though it feels like, despite all the fireworks, the show is a little bit running in place.
With the speed force dying and Barry's ability to access it fading, Caitlin (Danielle Panabaker) and Cisco (Carlos Valdes) equip Barry with a superhero fitbit that detects how much of his residual energy he is drawing from. Unfortunately, we also see that Barry's emotions also draw on the speed force, as evidenced by his monitor glowing red when he confronts Nash/Thawne. It's a fitbit, it's a mood ring– it's a floorwax, it's a dessert topping! Luckily, Cisco hits Thawne with a tranq gun before Barry kills him for comments about his daughter Nora.
Once subdued, Team Flash is able to scan Wells' brain patterns, finding that all of the other multiverse's brain patterns are imprinted on his, including Thawne, whose brain waves only appear in three dimensions. Using the MAD device they used to fight The Thinker, they plunge into Nash's memories, where Thawne is making him relive his worst moments to torture him, thereby gaining power and being able to take over.
There's a nice element of self-therapy here, as Nash has to exorcise his own personal demons and guilt in order to exorcise Thawne. It's a great lesson to us all when dealing with anxiety, grief and loss. It also brings to mind a classic scene in the pilot for Deep Space Nine when the wormhole aliens visit Ben Sisko's mind and how he constantly reflects on the loss of his wife at Wolf 359. "Why do you exist here?" they ask. Why do our memories of trauma and loss haunt us so much? Why do we spend so much time and energy reliving these painful memories?
Meanwhile, Mirror-Iris (Candice Patton) and Mirror-Kamilla (Victoria Park) have a new mission: track down a specific piece of technology to help Eva (Efrat Dor) escape her mirror dimension. Unfortunately/fortunately, a new villain named Sunshine (Natalie Sharp) wants the same tech, so it becomes a game of Iris waiting for the GCPD to catch her and recover the macguffin afterwards.
Among this, there's some good scenes. Sunshine is a fun villain, and Sharp is definitely sinking her teeth into the role. It's sad she's mostly written off as a villain of the week, because there's a spark of brilliance in the performance and character that could, nay, should mean bigger things.
But the bigger impact for the show is the team dynamics. Worrying about Barry's remaining speed force, Caitlyn/Killer Frost orders Barry to stay behind and let her deal with Sunshine. Always unable to let go (didn't we go through an entire half season arc about this pre-Crisis?) he has to jump in to save the day, even as Sunshine then knocks him completely on his ass.
But it seems Barry learns some lessons. So without using his speed, in his guise as Barry Allen, CSI, and working with the GCPD, they're able to lure Sunshine to Barry's lab, where he is able to block out all sunlight, making her powerless. I like seeing Barry Allen the smart guy with the good heart be a hero and not have to rely on his powers.
However, it's getting a little painful to see supposedly smart guy Barry continue to not recognize there's something seriously wrong with his wife. But it doesn't look like this is coming any time soon, as it appears in our next episode Iris is going to attempt to drain Flash of his remaining speed.