I haven't read the Lino yet, and I will when I'm done wading through the forum, but off the top of my head, to piggyback on Storm's idea... is there some action-driven thing, some tragedy or near-tragedy or horrible event, in which the "allies" must come to the aid of one another, console one another, etc... some external influence... the point being that we think these "allies" are the best of friends, always there for one another. Then the later betrayal will be that much more hurtful.

Cheers,
Michelle