Greek Betrayal as Plot Hook

When I was in college I was in an improv troupe. I loved that improv troupe. We met once a week for the better part of 4 years to do improv (read: tell stories) together. We started off doing out-of-the-box improv "games" and ended up eventually abandoning these in favor of something called long-form. In long form you basically just make up a 1 act play as you go. Or like, collaboratively write/act a screenplay on stage. It's fun.

By the end of things, we started to think about experimental ways to make interesting plot hooks. My favorite one we developed came from analyzing ancient Greek drama. So, in a lot old Greek plays in the first scene Character A is talking to Character B, but what we (and A) don't know is that B has already done something to betray A. And the rest of the play is A and the audience figuring that out. This is the precursor to In Media Res. OR is In Media Res. Whatever. What this meant in improv was:

Scene 1:

Performer A walks out and starts doing something. Let's say sweeping up.

Performer B walks out and does or says something. "Hey. I can finish sweeping up for you."

--So then what you do, either as Performer B, or as the whole group is figure out how "Hey. I can finish sweeping up for you." is ACTUALLY a betrayal. And that's it. You can easily spend an hour figuring out how that one sentence/action is a betrayal and resolving it. Like, maybe I know that there is gold hidden in the room and whoever sweeps up will find it. Maybe I know if you leave first, you'll be the one kidnapped instead of me. Maybe I need you to leave me alone with the broom cause there's micro-film inside the handle, and I'm a spy, and I'm framing you for its disappearance.

Which is to say, if you a DM needs to have a random non-combat encounter that is interesting, but can't think of something interesting at that exact moment, don't sweat it. Simply make that interaction mundane, then spend the adventure revealing how the mundane was ALREADY a betrayal of the PCs.