Upon triggering, half the flagstones at the characters' feet in whatever corridor or room the trap is in fall away, revealing a dark pit with no apparent bottom. Standing upon a stone seems to prevent it from falling until the character steps off, whereupon it tumbles away after a second or so. Characters must follow each other, hopping immediately from stone to stone, to get to a nearby ledge. Dex rolls or Saving throws are required for each jump. Magic or certain skills like climbing walls may help, as might throwing a rope with a grappling hook, etc. It will require ingenuity and cooperation to survive this. Optional: The darkness below is magical, and there is also a silence spell on the same area. The fall is not far, but any characters who slip into the darkness will seem like they have dropped to their doom.