It's in the Book by Mickey Spillane

Co-author’s note: It’s unclear when Mickey began this story, which I have developed from an unfinished typescript, but internal evidence suggests the 1980s, so I have made that the time period of the tale. M.A.C .
    C OPS ALWAYS COME IN TWOS. One will knock on the door, but a pair will come in, a duet on hand in case you get rowdy. One uniform drives the squad car, the other answers the radio. One plain-clothes dick asks the questions, the other takes the notes. Sometimes I think the only time they go solo is to the dentist. Or to bed. Or to kill themselves.
    I went out into the outer office where a client had been waiting for ten minutes for me to wrap up a phone call. I nodded to him, but the six-footer was already on his feet, brown shoes, brown suit, brown eyes, brown hair. It was a relief his name wasn’t Brown.
    I said, “I can see you now, Mr. Hanson.”
    At her reception desk to one side of my inner-office door, Velda—a raven-haired vision in a white blouse and black skirt—was giving me a faintly amused look that said she had made him, too.
    Mr. Hanson nodded back. There was no nervous smile, no anxiety in his manner at all. Generally, anybody needing a private investigator is not at ease. When I walked toward him, he extended a hand for me to shake, but I moved right past, going to the door and pulling it open.
    His partner was standing with his back to the wall, like a sentry, hands clasped behind his back. He was a little smaller than Hanson, wearing a different shade of brown, going wild with a tie of yellow and white stripes. Of course, he was younger, maybe thirty, where his partner was pushing forty.
    â€œWhy don’t you come in and join your buddy,” I said, and made an after-you gesture.
    This one didn’t smile either. He simply gave me a long look and, without nodding or saying a word, stepped inside and stood beside Hanson, like they were sharing the wrong end of a firing squad.
    Something was tickling one corner of Velda’s pretty mouth as I closed the door and marched the cops into my private office.
    I got behind my desk and waved at the client’s chairs, inviting them to sit down. But cops don’t like invitations and they stayed on their feet.
    Rocking back, I said, “You fellas aren’t flashing any warrants, meaning this isn’t a search party or an arrest. So have a seat.”
    Reluctantly, they did.
    Hanson’s partner, who looked like his feelings had been hurt, said, “How’d you make us?”
    I don’t know how to give enigmatic looks, so I said, “Come off it.”
    â€œWe could be businessmen.”
    â€œBusinessmen don’t wear guns on their hips, or if they do, they could afford a suit tailored for it. You’re too clean-cut to be hoods, but not enough to be feds. You’re either NYPD or visiting badges from Jersey.”
    This time they looked at each other and Hanson shrugged. Why fight it? They were cops with a job to do; this was nothing personal. He casually reached in a side suit coat pocket and flicked a folded hundred-dollar bill onto the desk as if leaving a generous tip.
    â€œOkay,” I said. “You have my attention.”
    â€œWe want to hire you.”
    The way he hated saying it made it tough for me to keep a straight face. “Who is we?”
    â€œYou said it before,” Hanson said. “NYPD.” He almost choked, getting that out .
    I pointed at the bill on the desktop. “Why the money?”
    â€œTo keep this matter legal. To insure confidentiality. Under your licensing arrangement with the state of New York, you guarantee that by acceptance of payment.”
    â€œAnd if I reject the offer?”
    For a moment I thought both of them finally would smile, but they stifled the effort, even if their eyes bore a hint of relief.
    Interesting — they wanted me to pass .
    So I picked up the hundred, filled out a receipt, and handed it to Hanson. He