Hawk appeared to be listening to the faintly audible ball game. And he was. If asked, he could give you the score and recap the last inning. He would also be able to tell you everything I said or Nevins said and how we looked when we said it.

—Hush Money

In Dashiell Hammett’s first Continental Op novel Red Harvest, the no name Op is summoned to Personville, a cesspool of a town called Poisonville by its inhabitants. Two factions, the capitalists and the gangsters, are competing to rule the place. The Op, charged with cleaning up the city, decides to set these factions against one another. He understands that tough choices have got to be made. “I’ve got hard skin all over what’s left of my soul,” he laments toward the end of the novel, after the violence he’s unleashed has taken its toll.

On first glance, Hammett’s Continental Operative is an unassuming-looking, pudgy, balding, middle-aged fellow who you might mistake for a shoe salesman. But if you went up against him, you found out this bastard was a cold-eyed son of a bitch with anthracite for a heart, an individual who, by his own admission, engaged in “necessary brutality.” Over more than seventy short stories and two novels, we don’t learn the Op’s real name, nor do we gain so much as a glimpse of insight into his personal life.

Hammett’s Op brings to mind another well-known enigmatic character—Hawk, the no-nonsense regulator in the Spenser novels. Robert Parker’s Spenser is  …