Mr. Hopkins’s plan of rooting for the Yankees in the first inning worked well for the team. The Yankees were on fire! The stadium was full, and the Yankees fans went crazy when the second runner scored to make it 2–0, Yankees.

“I guess they want payback for yesterday’s loss,” Kate said. “I’m rooting for the Mets, but as long as I’m watching the game with you, Dad, I don’t care who wins!”

“And I’m rooting for the Yankees,” Mike said. He took a big slurp of his drink through a red-and-white-striped straw. “But as long as I have my egg cream, I don’t care who wins!”

Mr. Hopkins ruffled Mike’s hair. “Then I guess we all win,” he said. “Except for your mother, Kate. What happened to her research?”

As they watched the game, Mike and Kate told Mr. Hopkins how the press box had been broken into and why they had thought it was connected to Mr. Hopkins’s mystery note. They also filled him in on their idea that Milo did it.

“I’d bet my plane ticket back to Los Angeles that Milo doesn’t have anything to do with it,” Mr. Hopkins said. “He’s been a friend of your mom’s forever.”

“Drat!” Kate said to Mike. “If Milo didn’t do it, we’re at a dead end! He was our only real lead. Our other suspect, Rocco Sampson, has an alibi!”

Even though it wasn’t a good day for catching the thief, it was a good day for the Yankees. The Mets just couldn’t get ahead in the game. They fought back in the fifth and sixth innings and got two runs. But the Yankees scored one more run in the seventh inning to pull ahead by one.

Nobody scored in the next inning, but the crowd exploded when the Yankees’ best hitter, Scooter Boyd, came up to bat with two outs and one runner on base. Mike jumped to his feet with the rest of the fans and clapped. “Come on, Scoot-er! Come on, Scoot-er!” they yelled.

Scooter took a few practice swings and dug his back foot into the dirt. The Mets pitcher fired a fastball straight at home plate.

SWISH!

Scooter swung and missed. But he connected on the very next pitch.

WHAP!

The ball looked like a line drive. As it sailed over the second baseman’s outstretched glove, Scooter ran for first. But the ball kept climbing and Scooter kept running. The ball sailed on! It flew over the right-field fence for a home run.

Scooter headed for second base. The other Yankees runner crossed home to score. Scooter crossed home plate with his arms stretched up. Another run for the Yankees! They were ahead by three now. The fans cheered and stomped. It looked like it was going to be a good day for Yankees fans.

Unfortunately for Kate, the Mets didn’t stage a rally. After a groundout and two strikeouts in the ninth, the game was over. The Yankees had won. And the Subway Series was tied at one game each. As fans headed for the exits, the song “New York, New York” drifted out of the stadium’s loudspeaker. Some fans swayed and sang along as they left the ballpark.

Mike, Kate, and Mr. Hopkins found their way to the subway station. Kate’s mom had to stay in the press box and work after the game, so the kids were going to have dinner with Mr. Hopkins. He’d take them to their hotel later that night.

After a bit of a wait, they pushed onto a number 4 subway train. It was packed with people returning to Manhattan from the game. As the train rumbled along, Mike stared out the windows as trees and buildings rushed by. Kate started to read a Subway Series program she had bought, but then nudged Mike after a few minutes.

“Look! There’s Rocco Sampson,” she said. Kate pointed to the far end of the subway car. Standing near the door was the manager of the Mets’ Home Run Apple. Just like yesterday, he was wearing a Yankees hat and a Mets jersey. “What’s he doing here?” Kate asked.

Mike shrugged. “He’s a Mets fan,” he said. “He went to the game just like we did!”

Kate studied Rocco. “If he gets off at Grand Central when we do, let’s follow him,” she said.

A few minutes later, the subway train screeched to a halt at Grand Central, and almost everyone got off. As Mike and Kate stepped onto the platform with Mr. Hopkins, they kept glancing back at Rocco. He had exited the train, too, and was walking behind them in the crowd.

As they wound their way through Grand Central, Mr. Hopkins stopped at an archway in front of the Oyster Bar & Restaurant. The long arches on either side of the walkway were made of glossy marble and curved along the wide tiled ceiling to pillars on all sides.

“Are we going to eat right now?” Mike asked. “That’s great! The subway ride made me hungry.”

“Soon!” Mr. Hopkins said. “We’re going to get takeout and have a picnic dinner in my hotel room. But we can get the food here.”

Kate glanced over her shoulder. Rocco was still behind them. He had just taken out his phone.

“Could you get the food, Dad?” she asked. “Mike and I want to hang out here and watch the people.”

“Okay,” Mr. Hopkins said. “I’ll be right back.”

Mr. Hopkins headed off to buy dinner. Kate leaned against the glossy marble of one of the archway’s pillars. She pretended to flip through the souvenir program she had bought at Yankee Stadium.

As she glanced up from her program, Rocco Sampson walked by. He had his phone pressed against his right ear and was talking to someone.

“There he is!” Mike whispered to Kate. They were just about to follow him when a loud group of girls passed through the hallway.

Rocco stopped walking and put a hand up to cover his left ear. Then he turned to face the wall on the other side of the archway. As soon as he did, Mike and Kate heard a voice in their ears.

“Nope, they didn’t suspect anything!” said the voice.

Mike and Kate looked around, but they couldn’t tell where the voice was coming from. Kate put a finger to her lips to tell Mike to stay quiet.

“Tomorrow night will be the big game,” the voice continued. “I set up a special surprise before the third inning!”

Kate stepped out of the archway to get a better look at the people around them. “Did you hear that?” she asked Mike. “Who was talking?”

“I don’t know,” Mike said. “Maybe that egg cream is giving us superpowers to hear people’s thoughts inside their heads.”

“Mike! This is serious!” Kate said.

Far across the passageway, Rocco was still facing the wall and talking into his phone.

“It’s him!” she said. “We’re hearing what Rocco is saying into his phone!”

Mike frowned. “He’s too far away,” he said, “and he’s facing the wall. It can’t possibly be his voice!”

A moment later, the girls finished passing by. Rocco turned back around, slipped the phone into his pocket, and walked up the hallway. The voice stopped.

Kate watched Rocco leave and studied the archway. She grabbed Mike by the shoulders and turned him around so he was facing the archway pillar.

“Wait here,” Kate said to Mike. “You can help me test out an idea.”

“Hey, it feels like I’m in a time-out!” Mike called from over his shoulder. “No fair!”

Kate ran across the hallway to the other side of the arch. She turned and faced a corner wall of the archway pillar. In a soft voice, she spoke directly into the wall.

“Mike, can you hear me?” she asked.

Mike’s voice came out of nowhere. “Loud and clear!”

“That’s good,” Kate’s voice said. “Because I have an idea who took my mom’s notes!”