The salesman got home late in the evening. For not waking his wife up, he takes his clothes off without turning on the light.

Just as he is about to get into bed, his wife asks him: "Will you, please, go to the drug store and get me some aspirin? I have such a headache, I can't sleep. And, please, don't turn on the light, it'll get worse."

So, in the dark, he dresses and goes to the drug store in the neighbourhood. There, he meets one of his friends who says: "Hi, I didn't know you were a postman."