The secretary and the wife

A married man was having an affair with his secretary.
One day they went to her place and made love all afternoon.
Exhausted, they fell asleep and woke up at 8 PM.
The man hurriedly dressed and told his lover to take his shoes outside and rub them in the grass and dirt.
He put on his shoes and drove home.
"Where have you been?" his wife demanded.
"I can't lie to you," he replied, "I'm having an affair with my secretary. We had sex all afternoon."
She looked down at his shoes and said: "You big liar! You've been playing golf!"