"They had to get it inside him in the first place," Yelena notes. "Unless they put it in his head before they did...whatever it is they did to him. Which is something I would not put past Valentina."

Put a kill switch in all of her test subjects, so they could be disposed of whenever she was done with them. A security measure against any of them ever gaining some independence.

"But this assumes he'd be willing to let anyone try, if there's something still there. I can probably convince him to do the scans, but brain surgery is a much bigger ask."