missing part:

> The helper gets on with the job. Moving quietly through your home, doing the work. Removing mounting plates, screwing in replacements with a cordless drill, testing each -- beep -- one, moving the ladder, sweeping cobwebs and dust away. All silently, with nary a peep out of them.

... until they eventually come to the alarm that was mounted near the light. The electrician did not know this, but the light was installed incorrectly, and its wires ere running just under the place where the new alarm was going to be installed.

When the helper installs the alarm, the screw goes in - and there is a loud snap and buzz, light blinks a few times and starts glowing really dimply. The helper ignores it - they were only told to install fire alarms. They put in the second screw and move on. Installing the smoke detector is a bit tricky, with the light out, strong smell of smoke and mounting plate deforming from heat, but the helper manages to do it - as they are pretty smart! Helper feels really good now that all the assigned tasks are done. They go to find the owner, but looks like he stepped out. No matter, helper will send the bill electronically for the job well done.