Who’s cheating?
“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.”