In the episode Safe, Mal comes back to rescue Simon.
SIMON Captain... why did you come back for us?
MAL You're on my crew.
SIMON Yeah, but you don't even like me. (beat) Why'd you come back?
MAL You're on my crew. Why we still talking about this? (walks off, over his shoulder) Chow's in ten. No need to dress.
Again in the episode Ariel, Mal threatens to allow Jayne to get sucked into space for betraying the Tams to the Alliance.
But then, at the beginning of the movie Serenity, Mal tells Simon, "I look out for me and mine. That don't include you unless I conjure it does."
I was wondering if there was any indication in the books or extra media that would indicate why Mal had this change of heart?