Cool air oozed from the darkness, bringing with it the smell of disinfectant and air conditioning.

We slipped inside and closed the door behind us.

“Hit the freakin’ lights!” Shelton does not love the dark.

“Shh. Hold on,” I whispered.

I groped the wall, finally found a panel of switches. Flipping several, I activated halogens overhead.

We stood in a windowless concrete chamber, empty but for a short staircase leading to a sturdy wooden door.

I bounded up the three treads, tested. The knob turned.

“Let’s go.” I motioned Hi to lead. The others followed.

“No talking until we get to the lab.”

My warning was unnecessary. No one was feeling chatty. We’d just committed a felony.

Emerging, we found ourselves in a small tiled lobby. Directly opposite was the building’s main entrance. In the rear left corner, a narrow staircase rose to a second floor. Gray light arrowed through dusty window blinds, throwing diagonal slashes across pale green walls, plastic trees, and a row of connected metal seats. The motif was corporate drab, as inviting as a lost baggage claim office.

Hi pointed to open double doors to our right. We scuttled through them, down a short hallway, through another set of doors, and into Lab Six.

The room had no windows, so we risked the lights. Ceiling fluorescents revealed a chamber the size of a large classroom. In the center were six workstations floor-bolted in two rows. Each station overflowed with equipment.

A stainless steel counter jutted from three walls of the room. Above it hung glass-fronted cabinets filled with beakers and other scientific apparatuses. Microscopes. Circular lenses. Gadgets whose functions were a mystery to me.

A Plexiglas enclosure occupied the right quarter of the room. Housing the more expensive technology, that section was locked and alarmed. Luckily, we needed nothing from there.

“Okay, hit it.” Shelton nudged Hi into action. “Find the sonicator.”

Moving to the third workstation in the second row, Hi removed a plastic cover from a small machine. “My precious,” he rasped in his best Gollum impression.

The contraption consisted of a small white sink backed by an LCD control panel. About the size of a microwave, it resembled a tiny top-loading washer with the cover removed.

“Sweet, eh?”

Hi’s father, Linus Stolowitski, was the mechanical engineer in charge of all LIRI scientific equipment. A technophile, he’d transmitted his love of gadgets to Hi.

“Sonicator is actually shorthand for ultrasonic cleaner.” Hi spoke in his very best church voice. Temple voice?

“What’s it do?” Shelton asked.

“The device uses ultrasound to clean objects.” Hi worked as he talked, filling the basin with fluid. “We’ll clamp the specimen an inch underwater.”

Shelton’s nose curled. “Whoa. That stuff smells like mega-strength Windex.”

“It’s cleaning solution,” Hi said. “I’ve set the machine’s frequency for the type of object we’re trying to clean, and for the type of substance we’re trying to remove. In this case, metal and dirt.”

Shelton looked lost. Ben looked bored.

“It’s like a sonar washing machine,” Hi explained. “The ultrasound enhances the cleaning solution’s effect.” He paused. “Do you guys know what ‘cavitation bubbles’ are?”

Nope.

“A sonicator has a transducer that produces ultrasonic waves in the fluid. That creates compression waves, which rip the fluid apart, leaving behind millions of microscopic ‘voids’ or ‘vacuum bubbles.’ That’s called cavitation.”

Okay. That was pretty cool.

“In our case, the cavitation bubbles will penetrate microscopic holes, cracks, and recesses in the dog tag. Then they’ll collapse, creating energy pockets. The reaction should remove even deeply embedded particles.”

“So when the mini-bubbles burst they blast away the gunk?” I summarized.

“Exacto.” Hi was enjoying his lecture. “Like tiny scrubbing dynamite.”

“Why’s the thing here?” Shelton asked.

“Sonicators are used for cleaning glasses, jewelry, and metal stuff like coins and watches. Even cell phone parts. Dentists, doctors, and hospitals use the gizmos to clean instruments.”

“And scientists.” Shelton had his answer.

Satisfied with the settings, Hi extended a hand in my direction. “The ring, Frodo?”

I pulled a plastic baggie from my pocket and removed the dog tag. Seeing the cement-like crust, my confidence faltered.

“This thing better work,” Shelton said. “We’re risking our butts to use it.”

“How long?” Ben asked, already restless.

“Fifteen minutes. Get out of my hair and it might go faster.”

Ben checked his watch, then wandered off the way we’d come in.

Shelton settled into a chair to wait.

Knowing we’d need something to view the tag once it was cleaned, I scanned the lab for optical equipment.

One counter had a Luxo lamp clamped to its top. The movable-arm magnifier lens was surrounded by a circular fluorescent bulb. Perfect. In a drawer I found several hand lenses and a penlight and placed them beside it. Viewing station complete.

“Five more minutes,” Hi chirped. His love of experiments had overridden his fear of capture.

“I’ll get Ben,” I volunteered.

I checked the hallway and lobby, but found both empty.

“Ben?” I hissed, as loudly as I dared.

No answer.

I considered yelling up the stairs, decided against it. Not wanting to stumble around in the dark, I returned to Lab Six.

A series of beeps was announcing the end of the cleaning cycle.

“All rriiighty then!” Hi removed the tag and ran it under cold water. I watched over his shoulder.

Much of the grime was gone. For the first time, I could make out indentations on the tag’s surface.

Hi wiped the tag with a paper towel and handed it to me. Excited, I placed it on the counter, thumbed the light switch, and positioned the Luxo.

“I can read something!” I confess. It was almost a squeal.

“What do you see?” Shelton crowded so close I could smell his deodorant.

“The bottom lettering is clearest. Hold on.” I adjusted the lens. Characters swam, then crystallized into focus. “C-A-T-H. Then an O, I think. I can’t get the rest.”

“Catholic,” Shelton guessed. “A soldier’s religion was stamped on the last line. What else?”

I squinted through the lens again. “Above that, more letters: O P-O-S.” Aha! “His blood type, right? O positive?”

“Gotta be.” Shelton thought for a moment. “Can you make out any numbers?”

“I think so. On the next two lines. But they’re really hard to see. Looks like the first string is nine digits long. Above that is a second sequence, looks like both letters and numbers.” Quick count. “Ten characters. Why?”

Shelton grinned and raised both hands to the sky. “Good morning, Vietnam!” he whisper-screamed, elongating the final word by a dozen syllables.

“How can you tell?” Hi asked. “You haven’t even looked.”

“Now it’s my turn to teach, sucker!” Beaming, Shelton threw an arm around Hi’s shoulders. He started to arm-wrap me but stopped short, self-conscious about my gender. The spontaneous move morphed into a head scratch.

Boys.

“We’ve got a nine-digit social security number and a ten-digit military service number. That’s rare.” Releasing Hi, Shelton pointed at the tag. “In the late sixties the armed forces switched from military ID numbers to social security numbers. But for several years they printed both, just to be safe.” Dramatic pause. “That occurred only during the Vietnam War.”

“Incredible,” I said. “We caught a big break there.”

“True,” Hi agreed. “Call me crazy, but couldn’t we solve this in an easier way?” He adopted a pensive look. “How about... oh, I don’t know, maybe just reading the guy’s name?”

Good point. Back to the magnifier.

As much as I raised and lowered the arm, I couldn’t bring the letters into focus. “There’s too much damage,” I said. “The lettering is obliterated.”

I flipped the tag indented side up. Vague symbols wavered under the lens.

“The reverse side’s a little easier to see. But the letters are backward. I can only make out an F on the next line up.”

“Focus on the top row,” Shelton urged. “That’s the soldier’s last name. Get that, we could investigate online.”

Using the penlight, I angled a beam across the tag. Letters appeared as shadows in the metal. “This is working. I see an N. Then a C. No, it’s an O.” I increased the angle of the penlight. “Then a T-A-E. The last is an H.”

I reversed the string in my mind. “Heaton.”

“Well, that’s a start.” Hi flicked a salute. “Nice to meet you, F. Heaton.”

I summarized aloud. “F. Heaton. Catholic. O positive blood. Served during the Vietnam War era.”

“Not bad,” Shelton said.

Not bad? I was psyched. We’d accomplished our goal. But our discovery only led to more questions.

Who was F. Heaton? Why was his dog tag buried on an uninhabited island? Where was he now?

I didn’t know. But I was determined to find out.

And it was time to go. Our luck couldn’t last forever.

We were repacking the sonicator when Ben burst through the double doors.

“Ben, the name was—”

He waved me off. “I found another lab upstairs. Locked, but I think it’s in use.” Ben was speaking to everyone, but looking at me. “You’ll want to see.”

“We got what we came for. We should leave before we’re nabbed.”

“Something’s in there. Something alive.”

“Why do you say that?”

“I heard barking.”