Objective is to find the ticking time bomb that been hidden in the hall before it detonates!
Clockwork kitchen timer that ticks
1) Choose a bomber to hide the bomb (clockwork kitchen timer)
2) Everyone leaves the hall so the bomber can hide the timer.
3) Set the timer.
4) Everyone comes back into the hall to search for the timer before time runs outs.
5) Repeat, finder of the bomb/timer becomes the next bomber.
Alt) Hide the timer before the start of the evening and during the evening announce that a bomb has been hidden in the hall.
This can be repeated during the evening.
If they listen they will hear the tick