Season 4: Episode 85: Oxy Moron
As Doug and Carrie's plane makes an unexpectedly rough landing, Doug takes the only available oxygen mask for himself and doesn't think twice about Carrie. She is hurt that he would think of himself first, while he doesn't think that he's done anything wrong. It's not until Carrie says that she will forever see him differently that Doug feels guilty for what he did and tries to prove to her that if her life were in danger, he would save her. Meanwhile, Spence needs to find a new place to live and ends up moving in with Danny Heffernan after things with the hot Brazilian exchange student don't go as he'd hoped.