One day John looks over the fence and spies Sam’s wife, undressed, watering the garden.
When Sam gets home from work, John brags to him that he’s seen his wife undressed.
Sam wants revenge, so that night creeps over to John’s yard and catches sight of John’s wife performing lovemaking.
The next day, Sam approaches John at the mailbox.
“Hey, I saw your wife performing lovemaking on you last night.”
“Ha ha, the joke’s on you,” John says, “I wasn’t home last night!”