A .45-caliber semiautomatic pistol fires a half-ounce lead cylinder at a speed of 579 miles per hour. If the bullet strikes a brick, it leaves a distinctive mark, a gouge surrounded by radiating cracks.

It’s almost evening. accompanied by Mark Levell, a Prohibition-era historian who has compiled files on more than two hundred crime sites in Chicago, I’ve trav eled to the city’s far North Side. The leafy streets and brick houses are serene. We park, discreetly, a few doors away from our destination, 2525 West Morse Avenue. We’ve come to see where Big Tim Murphy got it.

A New Yorker, I’m here to look for the fragments of reality behind the gangster myth. In my novels, I’ve treated both the urban mobsters and the freewheeling desperadoes who shot up the Depression. What has always interested me about the crime are those moments a man experiences—as he walks into a bank with a gun under his coat, for example—when the candlepower of reality is turned up to its maximum. In our collective dream, machine guns chatter harmlessly and diamond-studded hoodlums act out their roles in the outlaw fantasy. To uncover the gritty truth behind that dream, we need to peel back layers. Chicago, the center ring of America’s criminal big top, is certainly the place to do it.