"I Cannot Tell You a Lie" joke

A married man and his secretary were having a torrid affair. One
afternoon they couldn't contain their passion, so they rushed over to her place
where they spent the afternoon making passionate love. When they were
finished, they fell asleep, not waking until 8 o'clock that night.
They got dressed quickly. Then the man asked his secretary to take his
shoes outside and rub them on the lawn. Bewildered, she did as he asked,
thinking him pretty weird. The man finally got home and his wife met him at the
door. Upset, she asked where he'd been. The man replied, "I can not tell a lie.
My secretary and I are having an affair. Today we left work early, went to her place, spent the
afternoon making love, and then fell asleep. That's why I'm late."
The wife looked at him, took notice of his shoes, and yelled, "I can
see those are grass stains on your shoes. YOU LIAR! You've been playing golf
again, haven't you?"