A man wanted to determine if both his wife and mistress were faithful to him. So he decided to send them on the same cruise, then later question each one on the other's behavior.
When his wife returned, he asked her about the people on the trip in general, then casually asked her about the specific behavior of the passenger he knew to be his mistress. "She slept with nearly every man on the ship," his wife reported.
The disheartened man then rendezvoused with his cheating mistress to ask her the same questions about his wife.
"She was a real lady," his mistress said.
"How so?" the encouraged man asked.
"She came on board with her husband and never left his side."