"That wife of mine is a liar," said the angry husband to a sympathetic
pal seated next to him in the bar.

"How do you know?" the friend asked.

"She didn't come home last night and when I asked her where she'd been,
she said she had spent the night with her sister, Shirley."

"So?"

"So she's a liar. I spent the night with her sister, Shirley."