"Torrid Affair" 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 and didn't wake up till 8 o'clock.
They got dressed quickly. Then the man told his secretary to take his shoes outside and rub them on the lawn.
Bewildered, she does as he asks (thinking he's pretty weird).
The man finally gets home and his wife meets him at the door.
Upset, she asks where he's been.
The man replies "I cannot 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 then fell asleep.
That's why I'm late."
The wife looks at him, takes notice of his shoes and says, "I see those grass stains on your shoes. You've been playing golf again, haven't you!"