It's wrong to intentionally disrupt someone when they're working.
Wendel and Nancy are plumbers who like to prank each other, and Nancy is working on a pipe with a blowtorch.
Wendel wants to scare Nancy with a prank.
Wendel waits until Nancy is done with the blowtorch to prank Nancy.
Wendel decides to prank Nancy while she is soldering the pipe.
Nancy is startled, then laughs and says she'll get Wendel next time.
Nancy jumps in fear and burns her hand with the blowtorch.