ANOTHER SLUG CRACKLED BY. A third slammed through the Eagle’s fuselage immediately behind Isaac Bell and shook the back of his seat. A fourth screeched off the tip of the triangular steel king post above the wing. Heavy bullets—Marlin .45-70s, Bell guessed—Frost’s favorite. A fifth shot banged his rudder so hard, it rattled the control post. The gunfire was coming from behind him now. He had overflown Frost’s position and was moving out of range.

Bell spun the American Eagle on a dime and roared back, searching the busy river for the boat from which the gunman had fired. He had been flying up the middle of the mile-wide Hudson when the shooting started, equidistant between the pier-lined shores of Manhattan Island and New Jersey. The resultant half-mile range was too far from land for Frost to have done such accurate shooting. He was directly under Bell, somewhere in the gloom of smoke and haze, screened by the moving traffic of tugs, barges, car floats, lighters, ferries, launches, and sailing vessels.

Bell spotted a short, wide, flat gray hull scooting between a triple-track car float carrying half a freight train, and a three-masted schooner under clouds of sail. He descended to investigate. It was an oyster scow moving at an unusual rate of speed, trailing a long white wake and blue exhaust from a straining gasoline engine. The helmsman was hunched over his tiller in the stern. Its mast had been unstepped and shipped flat on the deck. A passenger was sprawled on his back beside the mast. He was a big man, Harry Frost’s size, who appeared to have fallen. But as Bell’s aeroplane caught up with the scow, he saw the sun glint on a long rifle.

Bell grabbed the control wheel in his left hand, drew his pistol with his right, and shoved the control post forward. If Harry Frost wondered why his wife’s yellow monoplane had circled back, he was about to get the surprise of his life when he learned that he had mistaken a similar profile in an identical color for Josephine’s Celere.

The Eagle dove at the oyster scow. Bell braced the automatic on the hull of the aeroplane, found the supine figure in his sights, and pulled the trigger three times. He saw one of his shots send wood chips flying from the deck and another tear a long furrow in the mast. The aeroplane lurched on an air current, and his third shot went wild.

The Eagle flew over the boat so close that Bell could hear the full-throated answering roar of Frost’s rifle, three shots fired so fast that the closely spaced holes they stitched in the wing a yard from Bell’s shoulder tore the fabric like a cannonball. So much for the surprise effect of two yellow aeroplanes.

“And you can shoot,” Bell muttered. “I’ll give you that.”

He had flown over and past the oyster scow in a flash. When he got the Eagle turned around again and headed back, he saw the scow fleeing at high speed toward Weehawken. Seen from above, a great sprawl of railroad track fanned from a dozen piers into rail yards and a vast thirty-acre stockyard packed with milling cows, where, in the thousands, they were herded off trains coming in from the west, bound for cattle boats that would ferry them across the river to Manhattan slaughterhouses.

Bell swooped after him, coming up from behind, firing his pistol again and again. But at such a low altitude, the flying machine bounced and slid in the smoky surface wind, making it impossible to steady his aim, while Harry Frost, firing from the more stable platform of the oyster scow, was able to send another astonishingly accurate hail of lead straight at him. Bell saw another hole appear in his wing. A slug fanned his cheek.

Then a lucky shot hit a wing stay.

The wire broke with a loud bang, as tons of tension were suddenly released. Bell held his breath, expecting the entire wing to collapse from lack of support. Tight turns would increase the tension. But he had to turn, and turn quickly, to make another pass at the fleeing scow before it reached the piers. If Harry Frost managed to get ashore, he stood a good chance of getting away. Bell flew after the scow, firing his nearly useless pistol and vowing that, if he got out of this fix alive, he would order the mechanicians to fit the American Eagle with a swivel mount for an autoload rifle.

Frost’s helmsmen steered for a pier where a gaff-rigged schooner was moored on one side and a four-hundred-foot steel-hull nitrate clipper was unloading guano on the other. The sailing ships screened the pier with forests of masts and thickets of crosstrees. It was impossible for Bell to shoot at Frost, much less attempt to land on the pier.

The oyster scow stopped alongside a ladder. Frost climbed fast as a grizzly. When he attained the pier’s deck, he stood still for a long moment, watching Bell circle overhead. Then he waved a triumphant good-bye and bolted toward the shore. Two big men in slouch hats—railroad company detectives—blocked his path. Frost flattened both yard bulls without breaking stride.

Bell’s eyes roved urgently over the industrial ground. There was no grass field in sight, of course. The rail yard was crisscrossed with freight trains, and the stockyards were thick with steers. He chose the only option. Battling a crosswind and hoping for eighty yards of open space, he tried to bring his aeroplane down on the pier that paralleled the one on which Frost had disembarked. A switch engine obligingly pulled a string of boxcars off it toward the yards. But stevedores scuttled about with wheelbarrows, and a team of horses ventured onto the pier, hauling a freight wagon.

The noisy racket of Bell’s Gnome engine, blatting loudly as he blipped it on and off to slow down, spooked the horses. They stopped dead in their tracks. When they saw the bright yellow monoplane dropping out of the sky, they reared and backed up. The stevedores dove for cover, clearing a path except for the wheelbarrows they abandoned.

The pier was eighty feet wide. The American Eagle’s wings spread forty feet. Bell brought her in right down the middle on a smooth wooden deck between two railroad tracks. His rubber-sprung wheels took the first impact, which forced them up to let the skids act as brakes. But the timbers were smoother than turf, and the Eagle glided like a skier on snow, losing almost no speed until it hit a wheelbarrow. The barrow tangled in the skids and caused the Eagle to tip forward onto her propeller. The nine-foot polished walnut airscrew snapped like a matchstick.

Bell jumped from the aeroplane and hit the ground running, extracting the empty magazine from his pistol and shoving in a fresh one. The ships moored along the pier that Frost had mounted from the scow blocked his view of the fleeing man. Bell was almost to the shore before he glimpsed Harry Frost, already on solid ground, running full tilt toward the stockyards.

Another railroad cop made the mistake of attempting to stop him. Frost knocked him down and jerked a revolver from the yard bull’s waistband. A fourth rail cop shouted at him and pulled a gun. Frost stopped, took careful aim, and shot him down. Now he stood his ground, turning on his heel, slowly, deliberately, daring any man to try to stop him.

Bell was a hundred yards behind, an impossibly long pistol shot, even with his modified No. 2 Browning. Pumping his long legs, he put on a burst of speed. At a distance of seventy-five yards, he aimed for Frost’s head, assuming that the marauder was wearing his bulletproof vest. It was still extreme range. He braced his pistol on a rock-steady forearm, exhaled, and smoothly curled his trigger finger. He was rewarded with a howl of pain.

Frost’s hand flew to his ear. The howl deepened to an angry animal roar, and he emptied the rail dick’s revolver in Bell’s direction. As the bullets whistled past, Bell fired again. Frost threw down his empty gun and ran toward the stockyards. Wild-eyed steers edged away. Frost vaulted a rail fence into their midst, and the animals stampeded from him, smashing into one another.

A steer jumped over the back of another and landed on the fence, knocking over a section. As fencing fell, animals crowded through the opening, leveling another section and then another, streaming in every direction, into the rail yard, onto a road to Weehawken, and toward the piers behind Bell. In seconds, hundreds of beef cattle were milling between him and Frost. Frost shoved through them, shouting and firing a gun he had pulled from his coat.

Bell was surrounded by horn-clashing, galloping animals. He attempted to clear a space by firing in the air. But for every fear-maddened creature that shied from the gunfire, another charged straight at him. He slipped on the dung-slicked cobblestones. A heel went out from under him, and he almost lost his footing. If he went down, he would be trampled to a pulp. An enormous whiteface steer came at him—a Texas Longhorn–Hereford crossbreed he knew well from his years in the West. Ordinarily more docile than they looked, this one was knocking smaller cows out of its way like bowling pins.

Bell holstered his pistol to free his hands. Seeing nothing to lose and his life to gain if he could only get out of the herd, he jumped with lightning speed, grabbing the whiteface’s horns with both hands and twisting himself over its head and onto its back. He clamped his knees with all his strength, grabbed the shaggy tuft between its horns with a steel fist, whipped off his flying helmet, and waved it like a bronco rider’s.

The frightened bucking steer kicked its legs into a frantic gallop, shoved through the writhing mob, leaped a tumbled length of fence, and thundered back into the now empty stockyard. Bell tumbled off and staggered to his feet. Harry Frost was nowhere to be seen.

He scoured the acres of cobblestoned corrals for Frost’s trampled body, peered into sheds and under the elevated office. He had no illusions about his own escape: he had been extremely lucky, and it was highly unlikely that Frost had been as fortunate. But he found no body, or even a dropped weapon or a torn coat or a mangled hat. It was as if the murderer had taken wing.

He kept hunting, as the stockmen began returning from the piers, the rail yards, and the city of Weehawken, driving captured steers that shambled into the yards too exhausted to pose any threat. Evening shadows cast by the stone cliffs of the Palisades were growing long when the Van Dorn detective stumbled upon a curved brick structure a few inches below the cobblestones. It was a circle of brick and mortar a full six feet in diameter, partly covered by a thick cast-iron disk. He knelt to inspect the disk. It had a date in raised numbers: 1877.

A stockman came along, cracking a whip. “What is this?” Bell demanded.

“Old manhole cover.”

“I see that. What does it cover?”

“Old sewer, I guess. There’s a few of ’em around. They used to drain the manure . . . Say, what the heck moved it? Must weigh a ton.”

“A strong man,” Bell mused. He peered into the darkness under it. He could see a brick-lined shaft. “Does it drain to the river?”

“Used to. Probably stops under one of them piers now. You see where they filled in the water and built the pier?”

Bell ran in search of a flashlight and hurried back with one he bought from a railroad cop. He lowered himself into the shaft, hunched under the low brick ceiling, and started walking. The tunnel ran straight and sloped slightly. It smelled of cow dung and decades of damp. And as the stockman predicted, after nearly a quarter mile he found a timber bisecting it vertically. Judging by the broken-brick rubble scattered around it, Bell reckoned it was a piling unknowingly driven down through the long-forgotten disused sewer by the builders of the pier.

The tall detective squeezed around it and walked toward the sound of rushing water. Now he could smell the river. The brick grew slippery, and the flashlight revealed streaks of moss, as if the walls were wetted twice daily when the tide rose. He passed another vertical timber and came abruptly to the mouth of the sewer. This would have been the end, underwater at high tide, originally extending into the river forty years ago before landfill extended the shore.

At his feet, a torrent of ebbing saltwater tide and freshwater river current raced toward the sea. Overhead, he saw the shadows of a dense frame of piles and timbers—the underbelly of the pier. He stepped onto a final crumbling lip of brick and looked around.

“What took you so long?” said a voice.

Isaac Bell had a split second to train his light on a bearded face, slick with blood, before Harry Frost hurled a pile-driver punch.