My solution for this jam was to provide a near-normal setting : "It's the world we live in, but there are monsters now and they can get you." I put the pressure on players to exercise their agency by removing the option to refer problems to authority: "The police and National Guard are busy with big stuff." And then to present a problem that they had to act to solve. "You've got a sick friend who needs medical attention." So it's absolutely a limited scenario, but there are a lot of details, left for the players to author in play - the nature and details of the monsters, the relationship to the sick friend, etc..
My goal was to leverage the familiarity of the real world and tighten the screws with familiar fraught situation stuff that they've seen in movies, on TV, or in books a million times - again, leveraging familiarity - to stay within the 10-30 minute time frame while still offering some narrative authority to the non-GM players.