The Big Black Book
In a small town in Texas, the local madam operated a telephone service. The police finally arrested her and seized her big black book in which her talent was listed. Each officer on the force was assigned a group of the names in it and told to check them out.
After a week, the Chief called a meeting to get their reports. When it became the turn of Detective Ralph to tell what he had found, he said, "I'm sorry, Chief, but I think I should disqualify myself. One of the ladies on whom I called is an eighty-four-year-old woman. She is so charming that I have to tell you that I have fallen in love with her."
"Damnation, boy!" exclaimed the Chief. "I sure am surprised at you. You've been a policeman almost all your life - and here you are, falling for the oldest trick in the book."