Together, Noodle and Tom’s dad raced across Yonkers Avenue, then took another left, which put them on Hayward Street, a narrow road just a few hundred yards from the parkway.

Halfway down the block, Tom’s dad stopped. His eyes cut back and forth in search of something. Then he stepped off the sidewalk and knelt to examine the tiny opening in the top of a manhole cover.

Noodle scooted closer to watch. “Are you ever gonna tell me what we’re doing?”

“If I explain it to you, Noodle, you’ll back out.”

“Oh, that makes me feel a whole lot better.”

Mr. Edison pulled out his ring of house keys and sifted through them until he found what looked like a small, nondescript key, the kind that might open a jewelry box.

“City workers enter the utility vault by using a lock pick.” Tom’s dad hooked the key underneath a small opening near the edge of the manhole cover. “We’ll have to improvise with a regular key. It’s just a matter of pushing back … the … catch.”

Then he jiggered the key until something underneath the cover clicked, and he was able to wedge it up a few inches with his fingers.

“Here. Come lend me a hand.”

Noodle squeezed his fingers in next to Tom’s dad’s and helped lift the cover a little bit higher. The metal was heavy, almost a hundred pounds, Noodle guessed, and it took all their combined strength to drag it over to the side.

Below the street, a paint-chipped ladder disappeared down into the darkness. Noodle leaned over and could barely make out a maze of pipes, ranging from a couple centimeters to about four feet in thickness.

“I used to work for the city as a low-level engineer before I started at Alset,” Tom’s dad explained as he descended the ladder, “so I know the whole infrastructure back and front. Up and down.” He was gone from sight now, but his voice rose, echoing up from the depths of the cavern. “Noodle, hurry up.”

Noodle wasn’t thrilled about this odd change in plans, but he didn’t have a choice if he wanted to get to Colby and Tom. He closed his eyes, grabbed hold of the ladder, and began to climb down. If there was one thing he was accustomed to doing, it was following an Edison down a blind alley toward almost certain trouble and probable injury.

“Wowzie,” he said as he joined Mr. E at the bottom of the ladder, which opened up into a tunnel. “We’re, like, in the city’s basement.” It smelled like a basement, too—wet and mildewed, cast in concrete, with pipes crisscrossing all around him and leading out in all different directions.

Tom’s dad was busy checking all the markings and symbols that were painted on the various pipes. “Gamma line, check. But we need to follow the beta line. Both empty into the Hudson River,” he muttered to himself.

“What do you mean, ‘empty into the Hudson River’?” asked Noodle, coughing through the dry lump of fear that had just formed in his throat.

“Each of these submains feeds into a main pipe. Just keep looking for the beta line.”

Noodle wasn’t sure how that answered his question, but he did what he was told, brushing some rust off one of the smaller aqueducts. Its symbol was a Greek letter that looked sort of like a cursive E.

After a few more minutes of searching, Noodle broke the silence. “I see B,” he called, as soon as he spied a large letter B chalked in white across the side of one of the tunnel’s larger pipes.

“Brilliant!” Tom’s dad answered. “You found it.”

With zero regard for his jacket, Tom’s dad bent below the dirty pipe to inspect its pressure gauge, his face and hands now completely covered in fine red powder.

“And when will it be an appropriate time for you to tell me what the heck we’re doing down here, Big T?”

“We’re going to get Tom and Colby, of course.” Mr. Edison reached toward a steering wheel–type device that was connected to a small circular door at the top of the pipe, and began to yank it left. “And we’re not waiting in an hour of traffic either.”

Hissing sounds filled the tunnel. A thick jet of steam shot out from the top of the aqueduct as Tom’s dad creaked open the rusty hatch.

“Ah!” he said as he took a deep inhale. “Brings me back to my days as a junior engineer. Weekends, we’d all get together for aqueduct races.”

Inside the pipe was a rushing stream of water.

“Ready to give it a go?”

“I don’t even know what an aqueduct race is, but it sounds exactly like something your kid would make me do.” Noodle took a couple steps back, unsure if Mr. E was serious with this plan. “And he usually has some pretty crazy ideas.”

“Just lie back and relax.” Tom’s dad grinned. “It’s easy.”

“Yeah. Piece of cake.”