“Run, Iris, Run” is episode sixteen of season four of The Flash.
Cisco and Harry are brainstorming ideas on how to protect the remaining bus metas. Harry suggests changing their bodies. Cisco says it’s late and no matter what. DeVoe has thought of everything. Like Thawne.
The next day, Harry says he’s invented an intelligence booster to be smarter than DeVoe. Cisco calls it a thinking cap; Harry says Cisco gave him the idea. He got the security footage on the day of the particle accelerator explosion, which shows DeVoe using his own thinking cap. Harry wants to do it, Iris and Caitlin think it’s worth exploring but Cisco thinks it’s too risky, as DeVoe’s changed him into a homicidal maniac. He won’t help. Ralph is unhappy and Harry says he’ll try anyway.
Iris heads after Ralph, trying to reassure him. He ends up telling her she’s always safe and sound whilst the rest of them are in the field.
Barry meets Joe at Jitters; Joe has talked to Singh about him coming back to CCPD. The mayor wants to sit down with the DeVoes. They’ll need to speak to Ralph about impersonating him. Barry tells him Ralph barely leaves S.T.A.R. Labs. Joe has a bad feeling another bus meta will show soon.
At a bank, a man with some kind of fire power is holding the place up, and melts his way into the vault. One of the customers tries to talk him out of it, but gets knocked down when he touches the man. However, the robber’s powers are now gone. The other man has gone.
Cisco and Joe are at the scene, and Cisco confirms the metas powers are gone. However, he’s not a bus meta; it seems he skipped town when the Flash showed up and only just came back.
Back at the lab, Caitlin can think of some ways powers could be lost. Cisco thinks the man who disappeared was responsible. They identify him as Matthew Kim, an EMT at Central City General. Iris volunteers to go with Joe.
Ralph is helping Harry with the thinking cap. It seems to be working when tried. Until it catches fire.
At the hospital, Iris is telling Joe that she isn’t afraid to go out in the field and asks what kind of leader puts everyone else’s life on the line but not their own. Joe reassures her she’s fearless. They go find Kim, who panics and assume they’re going to steal his powers. He holds a scalpel to Iris’s throat. Barry is summoned and moves Iris away from Kim. Then tries to follow. Only he’s lost his speed. And Iris has found it.
Ralph is terrified of leaving S.T.A.R. Labs. Barry has no powers; Iris has them but doesn’t know how to use them properly. And Cisco is worried if he helps build Harry’s thinking cap it will end badly.