As Yamamoto closed the drawer on the money, he had the eerie sensation of being watched. He looked across the desk into the bold gaze of a beautiful woman whose photographic portrait stood in a silver frame. He recognized Langner’s dark-haired daughter and admired how faithfully the photographer had captured her compelling eyes. She had inscribed it in a flowing hand “For Father, the ‘gunner’ who ‘dreads nought’!”

Yamamoto turned his attention to Langner’s bookshelves. Bound volumes of patent applications vied with novels for the space. The applications filed recently had been written on a typewriter. Yamamoto pulled volume after volume, working his way back to the last year that applications were submitted in longhand. He spread one on the designer’s desk, then chose a sheet of paper from a side drawer and a Waterman fountain pen with a gold nib. Referring repeatedly to the sample of handwriting, he forged a brief, incoherent letter. Ending it with the words “Forgive me,” he scrawled Arthur Langner’s signature.

He took the iodine and the ammonia into the gun designer’s washroom. With the butt of his Nambu pocket pistol he crushed the iodine crystals on the marble washstand and brushed the resultant powder into a shaving mug. He wiped the gun clean with the washroom towel, leaving a purplish smear on the cloth. Then he poured ammonia onto the iodine powder, stirring with Langner’s toothbrush until he had a thick paste of nitrogen iodide.

He propped open the lid of the grand piano, reached into the narrow end farthest from the keyboard, and smeared the paste on the closely bunched strings. After it dried, the explosive concoction would become unstable and extremely sensitive to impact. A gentle vibration would set off a loud bang and a flash. Alone, the explosion would damage little beyond the piano. But as a detonator, it would be deadly.

He placed the silk sack on top of the cast-iron frame, immediately above the strings. The sack contained enough Cordite MD smokeless powder to propel a twelve-pound shell two miles.

YAMAMOTO KENTA LEFT the Gun Factory the way he had entered, his eyes still stinging from the ammonia. Suddenly, things went wrong. The North Railroad Gate was blocked by an unexpected burst of late-night activity. Switch engines were huffing gondola cars in and out, attended by a horde of brakemen. He retreated deeper into the arsenal, past the powerhouse, through a maze of roads, buildings, and storage yards. Orienting himself by the powerhouse smokestacks and a pair of experimental radio-antenna towers silhouetted against the moonlit sky, he crossed a park and gardens bordered by handsome brick houses in which slept the families of the commandant and officers of the yard.

The ground rose higher here. To the northwest he glimpsed the Capitol looming over the city. He saw it as yet another symbol of America’s fearsome might. What other nation could have erected the largest cast-iron dome in the world at the same time they were fighting a bloody Civil War? He was almost to a side gate when a sentry surprised him on a narrow path.