There was artist who worked from a studio in his home. He specialized in nudes, and had been working on what he thought would be a masterpiece for several months now.
His model showed up and, after exchanging the usual greetings and small talk, she began to undress for the day's work.
He told her not to bother, since he felt pretty bad with a cold he had been fighting. He added that he would pay her for the day, but that she could just go home; he just wanted some hot tea and then, off to bed.
The model said, "Oh, please, let me fix it for you. It's the least I can do."
He agreed and told her to fix herself a cup too. They were sitting in the living room exchanging small talk and enjoying their tea, when he heard the front door open and close, then some familiar footsteps.
"Oh my God!" he whispered loudly, "It's my wife! Quick! Take all your clothes off."