Something has gone badly wrong with Yo-Yo’s powers in Agents of SHIELD season 7 – and it’s possible her powers have been stolen. Natalia Cordova-Buckley joined the SHIELD team in Agents of SHIELD season 3, and she’s since become a key Inhuman asset – as well as Mack’s lover.
Yo-Yo is ordinarily one of SHIELD’s most useful agents, able to move at speeds of around 400 miles per hour. Her super-speed lasts for as long as a single heartbeat, and she ultimately snaps back to where she began, making her movements impossible to track by conventional means. Special effects have typically rendered this as though she generates some sort of temporal field around herself, meaning time passes more slowly for Yo-Yo than for the rest of the world. For some reason, though, Yo-Yo’s powers appear to no longer be working in Agents of SHIELD season 7. Most fans have theorized this is related to the Shrikes, who infected her body in season 6 – but there is another, far more disturbing, possibility.
Agents of SHIELD season 7, episode 5 reintroduced a concept from previous seasons; the idea it is possible to transfer an Inhuman’s powers from one person to another, using some form of surgical procedure. This technique was innovated by Daniel Whitehall when he learned how to steal the Inhuman Jaiying’s healing powers. It’s possible a similar process has been used to steal Yo-Yo’s powers, and she is simply unaware of it.
If this theory is correct, only one person has had the opportunity to take Yo-Yo’s powers; Fitz. When he was first introduced in Agents of SHIELD season 1, Fitz was a naive but deeply ethical scientist who hated the compromises he was forced to make in the line of duty. But he’s become a lot darker over the years, especially after the events of Agents of SHIELD season 4. There, he was immersed in a false reality called the Framework; he became one of Hydra’s greatest leaders in that twisted timeline, and conducted horrific and agonizing experiments upon Inhumans. This “Doctor Fitz” persona will forever be a part of the SHIELD scientist’s psyche, and Fitz retains all this dark knowledge of Inhuman biology. It would certainly include Whitehall’s procedures, given that – in the Framework – Doctor Fitz stole the powers of countless Inhumans in order to give them to Aida.
The agents of SHIELD are essentially caught in a Time War, with the fate of all history at stake. Given that’s the case, Fitz could well have decided to steal Yo-Yo’s powers and use them to manipulate time around himself. This would fit with Simmons’ cryptic comment Fitz has had a long time to figure out how to stop the Chronicoms; he now has the ability to slow time around himself, perhaps even extending Yo-Yo’s temporal field so he has all the time in the world to work out how to save the day.
More: Agents of SHIELD Officially Changes The Marvel Timeline