“Uncle Donny!” Bell shouted over his shoulder as he swam after the submarine. “Pick me up.”

Darbee’s gasoline motor clattered, spewing blue smoke.

The submarine kept submerging. The top of the turret and the periscope tube were all that remained above the surface. The handrails around it, the periscope, and the hatch wheel Bell had tried to open left a wake up the channel, splashing like a mobile f ountain.

Darbee’s scow came alongside, and Bell climbed on, rolling over the low gunnel onto the flat deck. “After him!”

Darbee shoved his throttle forward. The motor got louder, the wooden boat trembled, and the old man muttered, “What do we do with him when we catch him?”

Bell heard gunfire crackling behind him. The cops running to the frame house to telephone for help dove behind shrubs. Pistol fire raked the lawn from every window in the house.

“Counterfeiters live there,” Uncle Darbee explained.

“Faster!” said Bell.

He jumped onto the square forward deck.

“Get me alongside of the turret.”

The mostly submerged Holland was headed toward the Upper Bay at six knots. Darbee fiddled with his motor. The noise deepened to an insistent growl, and the oyster scow doubled her speed. It halved the distance to the splashing handrails, halved it again, and pulled past the backwash of the submarine’s enormous propeller. Bell braced to jump to the conning tower. The wooden boat surged alongside. He could sense more than actually see the steel hull beneath the surface. He braced to jump, targeting the periscope tube, gambling that the thin tube was strong enough to hold him until he got a grip on the rails.

The Holland submarine disappeared.

One moment, the turret was just ahead of him. The next, it was gone, deep in the water. Bell could see trailing bubbles and the ripples from the propeller, but there was nothing to jump onto anymore, no turret, no rails, no periscope.

“Slow down,” Bell called to Darbee. “Follow his wake.”

Darbee throttled back to match the submarine’s six-knot speed.

Bell stood on the foredeck, watching the rhythmic swirls of propeller wash and signaling the old man when to nudge his tiller to the left or right. How the underwater ship was navigating its course was a mystery that was solved after they had gone half a mile. Shortly before the submarine reached the next bend in the channel, its periscope suddenly emerged from the water, and the submarine changed course.

The spy had plotted their route out of the Kill Van Kull by noting the time that would elapse between each turn. Bell signaled a similar change and the oyster scow turned with it. The periscope stayed above water. It swiveled around until its glass eye was facing him.

“Stop engine!” Bell shouted.

The oyster boat’s speed dropped as it drifted on momentum. Bell watched for signs that the Holland would back up or even turn around to ram them. But it held its course and pulled ahead of the scow, still showing its periscope.

“Darbee, did the test Holland you watched have a torpedo tube in back?”

“No,” Darbee answered to Bell’s relief, until he added, “I heard talk they might add one.”

“I can’t imagine he’d waste an entire torpedo on us.”

“Suppose not.”

“Speed up. Get closer.”

Ahead, the Kill took a sharp turn. The periscope swiveled around, and the unseen helmsman steered through it. Bell signaled for the oyster boat to accelerate. He drew within twenty yards of the stubby tube and the swirling propeller wash. But the water ahead was turning choppy as the Kill spread into the Upper Bay.

Staten Island and Bayonne fell behind. A chilly breeze cut through Bell’s wet clothes, and waves began curling over the periscope. Enormous bubbles burst on the surface, and he realized that the Holland was forcing air out of its floatation tanks and admitting water to descend deeper. The periscope dropped from sight. The windswept waves of the Upper Bay obliterated the swirling wake.

“He’s gone,” said Darbee.

Bell searched hopelessly. Three miles across the bay sprawled the dockyards of Brooklyn and beyond them low green hills. To his left, four or five miles to the northwest, Bell saw the tall buildings of lower Manhattan and the elegantly draped cables of the Brooklyn Bridge spanning the East River.

“Do you know where Catherine Slip is?”

Darbee swung his tiller. “What do you want there?”

“Dyname,” Bell answered. The fastest ship in New York, equipped with a telephone and a radio telegraph, and commanded by a high-ranking naval hero who could move quickly to rally the Navy against the spy’s submarine and radio the New Hampshire to rig torpedo nets before entering the port.

Darbee gave him a canvas pea jacket that smelled of mold. Bell stripped off his wet coat and shirt, dried out his Browning, and poured water out of his boots. The overpowered oyster scow covered the five miles to the Brooklyn Bridge in twenty minutes. But as they passed under the bridge, Bell’s heart sank. The battleship New Hampshire had already landed. It was moored to the pier closest to the way that held Hull 44. If 44 was O’Shay’s target, they were a pair of sitting ducks. Explosions on the floating ship would set the entire navy yard afire.

TO ISAAC BELL’S RELIEF, Dyname was at Catherine Slip.

He jumped from the oyster scow onto the nearest ladder, climbed onto the pier, crossed her gangway, and shoved through the door to Dyname’s main cabin. Captain Falconer was seated on the green leather banquette flanked by two of his yacht’s crewmen.

“Falconer. They’ve got a submarine.”

“So I am told,” said the Hero of Santiago with a grim nod at three Riker & Riker Protection Service gunmen who were covering the cabin with pistols and a sawed-off shotgun. Bell recognized the bodyguard, Plimpton, who had accompanied Herr Riker on the 20th Century Limited. Plimpton said, “You’re all wet, Mr. Bell, and you’ve lost your hat.”

HELLO, PLIMPTON.”

“Hands up.”

“Where’s O’Shay?”

“In the air!”

“Tell your boss that I owe him for an excellent emerald and I’m looking forward to paying him in person.”

“Now!”

“Do it, Bell,” Falconer said. “They’ve already shot my lieutenant and my engineer.”

Isaac Bell raised his hands, having stalled long enough to rate the opposition. Plimpton held a semiautomatic German Navy Luger like he knew his business. But the pretty-boy bruisers flanking him were out of their league. The elder, gingerly toting a sawed-off 20-gauge Remington, might pass for a small-town bank guard. The younger gripped his revolver like a bouncer in a YMCA. They were not on Falconer’s yacht due to a well-thought-out plan, Bell surmised. Something had gone wrong.

What had drawn them at the last moment to Dyname? Escape on the fastest ship in the harbor after O’Shay unleashed his torpedoes? But Dyname hadn’t the range to cross the Atlantic Ocean. Surely O’Shay had intended to take a liner to Europe, traveling with Katherine Dee under assumed names, or had booked secret passage on a freighter.

She was what went wrong, Bell realized. Katherine was wounded.

“Is the girl aboard?” he asked Falconer.

“She needs a doctor!” the boy with the shotgun blurted.

“Shut up, Bruce!” Plimpton growled.

“I’m aboard,” said Katherine Dee. She staggered up the companionway from Falconer’s private cabin. Disheveled, pale, and feverish, she looked like a child shaken from a deep sleep. Except for the hatred on her face. “Thanks to you,” she said bitterly to Bell. “You’re ruining everything.” She had held tight to her pistol when he had shot her in Barlowe’s jewelry shop. She raised it with a trembling hand and aimed it at him.

“Miss Dee!” said Bruce. “You shouldn’t be on your feet.”