Somehow, John and Harold end up swapping bodies. While they try to figure out how to get the situation reversed, it presents several logistical problems. As Finch said, the numbers never stop coming...but John with his knowledge of combat and tactics is now in a body not equipped to use those skills; and Finch is in a body that is physically capable of all of those things but in the hands of something lacking the knowledge to do them. How do they manage?

Bonus if Finch's back seizes badly at one point, and Harold (in John's body) has to help John deal with it. When they get things sorted, John asks Harold if there have been times he's been in that much pain and not said, and makes Harold promise not to do that again.