Hi Chris,
I'll give this a shot...
Anything where the world is stake - well, the stakes are just innate so you probably don't need to push too hard there.
In a post-plague world, lone survivors must stop a mass execution, but are caught up in a world-threatening conspiracy.
I'm playing around here.
I thought I'd lead with the lone survivors - the thief is one of them, right? As are the team?
Not sure what's happening with the mass execution but that seems to be the goal.
Perhaps make the goal positive? "must save innocent people from a mass execution".
or even "a thief must stop a mass execution of survivors"?
In a post-plague world, a thief must stop a mass execution of survivors, but is caught up in a world-threatening conspiracy.
Hmm... having him as a thief suggests a potential character arc of bad to good - which is good. He transforms. People love characters who change.
I dunno. That's all I could do with what I've got.
Not sure where the conflict is.
INTENTION: stop a mass execution.
OBSTACLE: A world-threatening conspiracy??
We need to get a bit more detailed and specific with what's standing in their way.
But yeah- sounds cool.
Good luck!