Nicky is de-aged. Could be gradual as a result of what happened in the lab, and the others observe it over time. Or there is another incident and when they rescue him he is roughly in his late teens, or twenty or so, but with all his memories intact. Joe is torn between wanting to fuck his fresh faced lover through the floor, and wanting to protect Nicky from everything (including him). Nicky realises he is going to have to seduce his lover if he is ever going to be with Joe again. But he has no game. Like none at all. Cue the others trying to help. (Bonus points if you can get Copley in on it.) Some Joe pov would be the icing on the cake.