“Don’t Run” is episode nine of season four of The Flash and the midseason finale.
Harry and Cisco are arguing as they decorate S.T.A.R. Labs for Christmas. Gypsy is apparently at work in the holidays. Ralph and Caitlin arrive and the other three make a reference to Killer Frost. Apparently, it was fun hanging around with her.
Barry and Iris are going through their wedding gifts. The final one is a set of knives with one missing and no card. Barry cleans up, without using his speed. Iris asks why he’s barely using his powers. Because he used to run as it felt good. When he’s around her, he doesn’t need to run to feel good.
DeVoe is having problems and his wife helps him. He says the problems with his fine motor skills are accelerating. Today is the day.
Harry finds Caitlin at Jitters; it seems Killer Frost has a drink named after her. Caitlin spent so long worried that Killer Frost would hurt other people; now it turns out they’d rather hang out with her alter ego. Harry is reassuring her when the door shatters and Amunet Black arrives.
Barry and Iris have returned 40 toasters Rory bought them that they realise must have been stolen when Barry gets hit by an energy blast from the Thinker. Caitlin tries to transform into Killer Frost but Amunet slaps a bracelet on her to prevent it. Barry ends up being caught by the Thinker.
Iris heads back to the labs and they talk about both abductions. The satellite will have problems tracking both Barry and Caitlin. Iris asks Cisco to vibe Barry. It doesn’t work. Barry is in the Thinker’s lab behind some kind of forcefield.
Amunet doesn’t want Killer Frost; she wants Caitlin. She has a patient, a new meta, who objected to being sold and there’s some metal stuck in his head. She wants Caitlin to fix him. The meta, Dominic, comes around after Amunet leaves and Caitlin talks to him. It seems he can read the minds of people he’s close enough to see.
The Thinker tells Barry he’s there for a reason. To be taught. Life 101; there are no happy endings. The doorbell goes to DeVoe’s house; Joe is outside. DeVoe greets Joe and knows Harry is hiding outside with a gun. And DeVoe is perfectly willing to let Joe search his home without a search warrant. Marlize, meanwhile, tells Barry his skills can’t defeat the barrier. And she isn’t her husband’s assistant; she’s his partner. She’s willing to sacrifice everything for her marriage.
The problem with trying to use the satellite to search for Barry and Caitlin’s signatures at the same time is it can’t. Iris will have to choose. And Caitlin gets a pep talk about how good she is, even not as Killer Frost, from Amunet Black.
DeVoe has put his plan into motion and things are looking bad leading into “The Trial of The Flash”.