Barry is given a "Speed Gauge" by Cisco and Caitlen, which is a device to monitor his speed to prevent him from using up his reserves of Speed Force energy. Then, Caitlen and Cisco figure a way to stop Nash's body from being taken over by Thawne’s consciousness, however, the Eobard possessed Wells escapes and attempts to escape in the Time Sphere, but Barry is able to stop him. With time running out until Eobard fully takes over Nash’s body, Cisco decides to perform an Exorcism to rid Nash of Eobard’s consciousness. Meanwhile, at the CCPD, Joe and Singh suspect a mole within the department. Elsewhere, Eva sends Mirror Iris and a newly created mirror clone of Kamilla to steal a Prismatic Refractor from Mercury Labs that she needs for her "long term plans". During the heist, they are attacked by another Black Hole assassin going by the alias of "Sunshine", who is stopped by Frost and Barry. To ensure he has enough speed to face Sunshine, Barry injected himself with Velocity-X after ignoring Caitlin's advice, and his body rejects it. The team decides to turn the Prismatic Refractor into A.R.G.U.S. for safekeeping, and uses this transfer as a trap for Sunshine. The trap is sprung when Sunshine is lured into Barry’s CSI lab by Joe, Singh and Barry, and all the windows are closed leaving Sunshine powerless. Back at Star Labs, Cecile realizes that Thawne is trapping Nash in a loop of his past memories. Barry suggests he, Cisco and Cecile enter Nash's mind to help. While there, Cisco encourages a reluctant Nash to confront his memories while Thawne taunts Barry about his daughter Nora. To conquer his fear and emotions, Nash relives his memory of Maia dieing on Earth-13 one year ago, Maia is a doppelgänger of Allegra from Earth-712 and his daughter figure. Having overcome his fear and accepting his responsibility for Maia’s death, Nash expels Eobard’s consciousness from his mind, and back into the Negative Speed Force. Later, Cisco informs Nash that the minds of the previous Wells will still be in his head, and Barry apologises to Caitlin for using Velocity-X against her advice. Then, he explains his idea for using Nora's diary to find how to create a Speed Force. Finally, Mirror Iris and Mirror Kamilla bring back the Prismatic Refractor to Eva who plans to use it as part of her escape.