Diwali evening. The fairy lights are dead.

A hundred-bulb string on the balcony, dark, and guests arriving in an hour. One break somewhere along the wire is killing the whole thing. With the little tester in your hand, the wire beeps at every point before the break and stays silent after it.

So you start where everyone starts: at the plug. Bulb 1, beep. Bulb 2, beep. Bulb 3, beep.