On the morning of February 14, 1929, seven men waiting for a whiskey delivery in a garage at 2122 North Clark Street in Chicago were lined up against a brick wall by men dressed as police and cut down with Thompson submachine guns. One of them, Frank Gusenberg, lived long enough to tell real officers that no one had shot him. The target, North Side Gang boss Bugs Moran, was running late, saw the uniforms, and went for coffee instead. From hiding he told reporters that only Capone killed like that.

This episode traces how Al Capone reached that morning. He inherited the Chicago Outfit from Johnny Torrio in 1925, built a bootlegging business the government estimated at $105 million a year by 1926, and fought Moran over hijacked shipments of Old Log Cabin whiskey. It then follows the fallout: a horrified public, pressure from fellow crime bosses, and a federal case that reached him through his spending. Capone had a Florida alibi for the killings. He had none for his tax returns.

• The Outfit spent an estimated $15 million a year on bribes and carried a weekly payroll of $300,000.
• In 1926 a convoy of ten cars fired more than a thousand rounds into the Hawthorne Hotel in Cicero while Capone ate, and a bodyguard pushed him to the floor.
• Ballistics pioneer Calvin Goddard used a comparison microscope to show that Chicago police guns had not fired the garage bullets, and the trail led to hired gunman Fred Burke.
• After learning that three of his own men were plotting against him, Capone hosted a dinner in their honor and beat them to death with a baseball bat.
• IRS agent Frank Wilson built the case that convicted Capone in 1931 on 22 counts of tax fraud, and the massacre’s machine guns helped bring about the National Firearms Act of 1934.