He swung his barrel in Bell’s direction and opened fire. Braced on the solid roof of the armory, he was even more accurate than he had been from the oyster boat. Two slugs stitched through the fuselage directly behind the controls, and Bell knew that only the extraordinary speed of his dive had saved him when Frost underestimated how swiftly he would pass.

Now it was his turn. Waiting until his spinning propeller was clear of the field of fire, the tall detective triggered his Remington. Stone chips flew in Frost’s face, and he dropped his rifle and fell backwards.

Isaac Bell turned the Eagle sharply—too sharply—felt it start to spin, corrected before he lost control, and swept back at the armory. Frost was scrambling across the roof, leaping over the bodies of two fallen detectives. He had left his rifle where he had dropped it and was holding a hand to his eye. Bell fired twice. One shot shattered glass in the structure that housed the elevator machinery. The other nicked the heel of Frost’s boot. The impact of the powerful centerfire .35 caliber slug knocked the big man off his feet.

Bell wrenched the Eagle around again, ignoring the protesting shriek of wind in the stays and an ominous grinding sound that vibrated through the controls, and raced back at the red brick building to finish him off. Across the roof, the door of the stair house flew open. Soldiers with long, clumsy rifles tumbled through it and fanned out, forcing Bell to hold his fire to avoid hitting them. Frost ducked behind the elevator house. As Bell roared past, he saw the killer open a door and slip inside.

He looked down at the avenue in front of the building, saw that Josephine had alighted and that there was space for him. Down he went, blipping his motor. He hit the cobblestones hard, spun half around, recovered, and, when the tail skid had slowed him nearly to a stop, jumped down and ran up the front steps of the armory, drawing his pistol.

An honor guard of soldiers in dress uniforms holding rifles at port arms blocked his way.

“Van Dorn!” Bell addressed their sergeant, a decorated man of action whose chestful of battle ribbons included the blue-and-yellow Spanish-American War Marine Corps Spanish Campaign Service Medal. “There’s a murderer in the elevator house. Follow me!”

The old veteran sprang into action, running after the tall detective and calling upon his men. The inside of the armory was an enormous cathedral-like drill space as wide as the building and half as deep. The coffered ceiling rose as high as the roof. Bell raced to the elevator and stair shafts. The elevator doors were closed, and the brass arrow that indicated its location showed that the car was at the top of the shaft.

“Two men here!” he ordered. “Don’t let him out if the car descends. The rest, follow me.”