Locked Room: Mystery

Why would you slip a Mickey to an entire crowd full of people, including all the waiters and cooks and so on, lock the doors on the restaurant and pull down the curtains, and then let them recover themselves after the drug wore off, apparently with nothing changed for the worse? Even more of a question--how? How could you even get everyone? Either through intercepting some food or drink item from every person, or by aerosol dispersal. Why these people? Why this place? Why why why?


Inspiration: "Absurd" - Fluke
Story potential: Medium
Notes: Mystery, could be combined with many other genres/plots.