Barry turns to drastic measures to keep his speed and Thawne plans a rematch with him.
- 13 Is Unlucky: Nash lost his adoptive daughter on Earth-13.
- Bait-and-Switch Comment: Cisco's comment implies that he knows about another source of Speed Forces, but the only known creator so far is Thawne.
- Big Bad Ensemble: This episode confirms that Carver and Eva are working independently of each other.
- Big "NO!": Thawne shouts a "No!" while being expelled from Nash's body. It can be heard for a while when Barry and Cisco leave his body too.
- Blood Knight: Thawne is itching for another fight with Barry.
- The Bus Came Back: David Singh returns.
- Call-Back: Once again, using a combination of Cecile's powers and a cerebral device, Barry (and Cisco this time) venture into the mind of an ally to prevent his body from being completely taken over by the Big Bad, and are successful just as before—seemingly defeating the villain for good. They even note the same device is used.
- Canon Foreigner: Sunshine is an entirely original character for the Arrowverse.
- The Chains of Commanding: Singh tells Joe not to openly tell his men that there is a traitor among them as it could make them doubt him.
- Chekhov's Gun: Cecile uses the Spirit Board she brought earlier to knock Thawne out before he could attack Cisco.
- Chekhov's Boomerang:
- The Cerebral inhibitor is used for a similar purpose to when Barry went to DeVoe's mind.
- Barry thought about using Nora's diary to find how to create a Speed Force.
- Co-Dragons: Mirror Iris and Mirror Kamilla act as these for Eva.
- Continuity Nod:
- While impersonating Nash in his body, Thawne mentions the various Wellses, like the wizard, the New Yorker, among others.
- Barry mentions that Thawne isn't a real Wells because he murdered and replaced a real Harrison Wells.
- Mirror Iris reminds Barry of the time he was awarded a medal not as the Flash, but as Barry Allen.
- The symbols on the device Maya was trying to open resemble the symbols used by the Monitor on the prison of his anti-matter counterpart. This explains why Nash has such a grudge against Mar Novu.
- Cruel and Unusual Death: Sunshine kills people by frying their heads.
- The Disembodied: Barry and Cisco suspect this to be the fate of Thawne following the titular exorcism, despite not being able to trace any negative tachyons around Earth.
- Death of a Child: Brought up several times throughout the episode.
- Disney Villain Death: Maya, Nash's adoptive daughter, died by falling off the cliff in Earth-13.
- Emotion Eater: Thawne thrives on negative emotions. At the end, the heroes are able to expell him being overcoming them.
- Flashback: To Nash meeting a young Maya.
- Go Through Me: Barry doesn't let Thawne go after Nash.
- Guile Hero: Just as Mirror Iris suggested, Barry defeats Sunshine with his smarts instead of his speed: realizing the extent of her powers, he lures her into a trap he set up in the crime lab where the entire room was shuttered down and becomes void of all sunlight.
- The Heartless: Whatever Thawne has been reduced to, he's now capable of possessing people by feeding on their negative emotions.
- Joker Immunity: Even when Thawne is expelled from Nash, no one on Team Flash believes for a minute that he's gone for good, since he has already been erased from existence twice.
- Kick the Dog: Thawne repeatedly brings up Nora's death to torment Barry and breaks Nash's mind by reminding him of Maya's death.
- Logical Weakness: Sunshine is powerless without sunlight, so Barry tricks her into going to his lab and covers the windows to block the sunlight.
- Madness Mantra: "It wasn't my fault." is what Nash keeps repeating while being trapped inside his worst memory. At the end, he comes to accept the fact that it was his fault.
- Master Actor: Thawne fools the team by acting as Nash regaining control at the beginning of the episode.
- Mind Hive: Somehow, the collapse of the multiverse caused the minds of all the versions of Harrison Wells to be crammed into Nash's.
- Mind Rape: Thawne attempts to trap Nash in the consciousness of his own body forever, eternally filled with the sorrow and guilt of failing to save Maya.
- My Greatest Failure: Nash is tormented by the death of Maya, Allegra's doppelgänger and his daughter figure, during an expedition.
- My Greatest Second Chance: Both Cisco and Harry encourage Wells to try and connect with Allegra, to make up for Maya's death.
- Mythology Gag: Nash notes he previously used the neuro-splicer on Earth-26 to stop an invasion of "psychic starfish" — presumably that Earth's counterpart to Starro.
- Not Quite Dead: The Wells doppelgangers were sent to Nash's mind. Harry appears to encourage Nash to follow Ramon's advice, which indicates that he is the real one.
- Out-of-Character Alert: Joe becomes suspicious of Mirror Iris afer seeing her not being affectionate to Barry outside of when she is impersonating Iris and she doesn't follow Barry.
- Person as Verb: Cisco describes Thawne as having "Linda Blaired" Nash.
- Race Against the Clock: Barry has to find a way to keep his powers before Thawne can use his Negative Speed Force to kill everyone. By the episode's end, Barry still doesn't have his powers, but Thawne has been defeated, for now at least.
- "The Reason You Suck" Speech: Eobard gives Barry one of these, preying on all of Barry's insecurities and regrets about Nora. Later, Barry delivers an epic one to Thawne.
- The Reveal:
- Mirror Iris was created by Eva.
- Allegra's doppelganger was called Maya and was Nash's adoptive daughter.
- The various Wells doppelgangers are still living in Nash's mind.
- Shout-Out:
- There's an allusion to the Signature Line of Fight Club, and Cisco compares Nash's situation with Tyler Durden, only x1000.
- Barry and Cisco calling Thawne Voldemort.
- The episode's climax is similar to a scene in Indiana Jones and the Last Crusade, where Indy has a precious McGuffin while trapped in a Literal Cliffhanger, and Henry Jones Sr. is trying to save him. The difference here is that the Nash that told his daughter to let go of the artifact is the present Nash (not the one in the flashback), and Maya did fall to her death.
- Shut Up, Hannibal!: When Thawne brings up Nora to hurt Barry and to state that he and Nash are pathetic for grieving their deceased daughters, Barry tells him that their emotions can help them overcome obstacles, including him. Thawne gets expelled from Nash's body.
- Spotting the Thread: Joe might be after having to tell Mirror Iris to go to Barry.
- Uncertain Doom: It is unknown what happened to the original Kamilla.
- Villain Has a Point: Mirror Iris reminds Barry that he already hunted down villains back before being The Flash and he can use his intelligence to use Thawne and Sunshine's weaknesses.
- Wham Shot: Nash sees Harry encouraging him to follow Cisco's advice of befriending Allegra by seeing her as her own person.
- What the Hell, Hero?: Caitlin calls out Barry on losing his temper and almost killing Thawne, which means he would've also killed Nash as well since Thawne is inhabiting his body. She is also quite angry when he suggests taking Velocity X to help with his speed problem.
- You Are Better Than You Think You Are: Mirror Iris delivers quite the monologue to Barry about how he has always been a hero long before he got his super-speed, no doubt drawing from Iris's memories to get through to Barry. This inspires Barry to stop Sunshine without having to use his speed.
- You Are Not Alone: To help Nash finally cope with his grief, Cisco promises him they will be waiting for him.
