Samantha, like many mothers in the 1960s, sends out Tabitha's diapers to be laundered by a cleaning service. Diaper Dan arrives regularly, collects the dirty diapers and brings back the clean ones. The trouble is, Diaper Dan isn't quite what he appears to be as he has planted a microphone in a rattle he gave to Tabitha as a gift in order to evavesdrop on Darrin and Samantha's conversations for a rival advertising company.
Darrin and Larry cannot believe their eyes or their ears when the slogans that Darrin has worked on for a client selling pens turns up BEFORE he has delivered the pitch! When the same thing happens again and again, Darrin and Samantha argue when he accuses her of blabbing his slogans, which are supposed to be top-secret, to other people. Needless to say, Samantha is FAR from impressed at the accusation.
When the bug is finally found in Tabitha's rattle, Samantha and Endora have a great time giving Dan a few problems of his own which make it necessary for him to go on stress leave.