I think this is …”

Tom’s voice died in the air as he stared into the trunk. His father had materialized at his side and placed an encouraging hand on his shoulder.

“Go on,” he said. “I think you might be right.”

The book inside was beautiful, leather-bound and heavy, with a velvet padding along the inside cover. Its parchment pages were thick and yellowed with age.

Tom turned to the first page, a scripted introduction written with a quill pen.

“ ‘Herein lies what we believe to be the most incredible scientific discovery ever made by man,’ ” Tom read aloud.

By now, Noodle and Colby had taken a break from their treasure games to squeeze in behind him.

“ ‘By reading on, you accept the responsibility to guard this book’s most precious secrets with integrity and the utmost humility,’ ” he continued. “ ‘And though there will undoubtedly arise the urge to use the formula for one’s own greed and wealth, you must never succumb to its intoxicating powers, for knowledge is the most priceless treasure of all.’ ”

And then, in faded blue ink, was the signature:

Thomas Alya Edison
Sub Rosa Member
23 August, 1912

With shaking hands, Tom turned the page to reveal a complicated-looking formula, one of many, written below several lines of text.

Within the earth’s most stable elements, there exists the potential for purification, both physical and spiritual, it began.

“It reads like a symphony on paper,” his father said softly as he digested the book’s complex equations and diagrams.

For several minutes, none of them spoke as Tom flipped through the book. Every so often, his father would gasp at some particular piece of scientific brilliance or shake his head in awe.

The reverent moment was finally broken by a loud tramping of footsteps that shook the ceiling.

“Someone’s back,” said Mr. Edison with a nervous glance toward the room’s entrance. “We need to get the book out of here.”

“Wait! We gotta grab some loot first!” Broken from her trance, Colby unzipped her backpack and was about to start filling it with gold.

“Colby, no!” Mr. Edison snapped. “No one can know about this place.”

“Just a couple pieces, Mr. E!” begged Noodle. “Cash flow’s a little tight in the Zuckerberg household these days.”

But there was simply no arguing with Mr. Edison.

“The book comes with us and nothing else,” he said, shaking his head as he watched the kids with intense hawk eyes. “We’re the new Sub Rosa now, and it’s up to us to protect the secret.”

As hard as it was to admit, Tom couldn’t have agreed with his father any more.

“Come on.” Tucking the book under his arm, he ran toward the room’s entrance. “We really can’t afford to get caught right now.”

Together they ascended the stairs all the way back to the parlor, where they were met by Hannah’s voice, wafting in from down the hall.

“Now, up ahead, we have Mr. Irving’s parlor. Which, if you’ll look toward your left, still contains all of the house’s original furniture.”

“Tom, the key!” hissed his panicked father, snapping his fingers. He knew that once Hannah saw those fireplace stairs, her next phone call would be to the police.

Tom fumbled the key out of his pocket, dropping it from his sweaty hands. It clinked against the cement floor, bouncing toward the exposed steps.

With the grace of six years of gymnastics, Colby dove and caught it, her arm extended over the floor’s edge, inches above the staircase.

“Nice grab!” said Tom, then snatched the key from her and quickly jammed it into the fireplace lock. He turned it to the left, and the dull rumbling in the walls began again.

From way down below, they could hear the section of floor begin to rise. Not quickly enough, however, as the tour group was now just a few feet from turning the corner and catching them.

“Mr. E, what do we do?” asked Colby.

“Let’s get out of here,” said Tom, nodding to a door across the room.

Thinking fast, Noodle ducked his entire head into his sweatshirt and raced out into the hallway, waving his hands in the air like an escaped mental patient.

“Beware the ghost of the Headless Horseman!” he groaned at the top of his lungs, frightening the entire tour group. Several old ladies screeched in terror.

“That is not funny, young man,” said an irate Hannah. “Not funny at all.”

“Where is Ichabod Crane?” Noodle groaned in response.

In the parlor, the spiral staircase had now disappeared—and, along with it, the secrets of the Sub Rosa.

Trying not to laugh, Tom, Colby, and Tom’s dad casually walked unseen through the side door and headed back to the car to wait for Noodle, who was busy being chastised by the extremely upset tour guide.

Still, it could have been worse. A lot worse.