“Where is he?” Mike asked. “We need to get your mom’s notes back!”

It was the next day, just around lunchtime. Mike and Kate were in Monument Park at Yankee Stadium. They were crouched behind a big stone wall.

“Shhh!” Kate said. “We have to hide and be quiet so we can spot him first! Then I can call my mom.”

The second Subway Series game was due to start in about an hour. Fans walked through Monument Park, checking out the plaques and special monuments to famous Yankee players, owners, and managers. A little while before, Mike, Kate, and Mrs. Hopkins had taken the number 4 subway line to Yankee Stadium from their hotel near Grand Central Terminal.

After the first Subway Series game the night before, Mike and Kate had shown Mrs. Hopkins the note and told her their theory about her stolen research. They agreed that Kate and Mike would look for the man at Yankee Stadium before the second game. If they spotted him, Kate would call Mrs. Hopkins in the press box and she’d come down.

Mike and Kate kept an eye on the fans. They were on the lookout for someone in a Mets jersey and a Yankees hat. Out on the field, the Mets were taking batting practice before the game.

“Hey, there’s Babe Ruth!” Mike said.

The last time Mike and Kate had visited Yankee Stadium, they solved the mystery of Babe Ruth’s ghost.

“That’s not Babe Ruth, or even the ghost of Babe Ruth,” Kate whispered. She looked at a large red granite stone with the Yankee slugger’s name on it. “That’s just his monument!”

Mike shrugged. “It still counts as Babe Ruth to me,” he said.

They watched one fan after another enter Monument Park through a door at the far end. But none looked like their thief.

“Hey, look!” Mike said. He pointed to a man who had just stepped through the door.

Kate squinted. “That’s not him,” she said. “He’s wearing a Yankees hat and shirt! Plus, he doesn’t have sunglasses. We have to keep looking.”

“Okay,” Mike said. “If we can’t catch him now, I guess we’ll wait until later. Hey, that reminds me. What did the baseball glove say to the ball?”

“I don’t know, Mike,” Kate said. “What?”

“Catch you later!” Mike whispered. He nudged Kate. “Get it? That’s what we’re going to do to the thief!”

Kate rolled her eyes. “Ha-ha!” she said. “That’s funny. But it’s no joke that we need to get my mom’s notes back! Let’s keep our eyes open!”

They continued to scan the crowd. Since it was almost game time, it was getting busier.

Suddenly, Mike ducked down. “There he is!” he said. “That’s got to be him.”

Kate glanced at the doorway. A man wearing a Yankees hat and a Mets jersey had just entered the park. He had sunglasses on and dark hair. The man seemed to be looking around at the other fans as if he was searching for someone.

Kate and Mike moved to the far corner of Monument Park and hid behind a group of people.

“Aren’t you supposed to call your mom?” Mike asked.

“Let’s wait a little bit longer,” Kate said. “I want to make sure it’s the right person before I call her.”

Announcements boomed over the loudspeaker, and fans filled up the seats in the stadium. Mike and Kate kept their eye on the thief as he circled the park. They stayed out of his line of sight, hiding behind the wall or monuments as needed. Finally, he stopped near the front wall and looked at his wrist.

“His watch!” Mike said as he shook Kate’s shoulder. “It’s silver with a blue and white band. Just like the hot-dog vendor said! It’s got to be him!”

“Wow, you’re right!” Kate said.

Mike squinted a little. “I can’t really see his face, but he reminds me of someone I’ve seen before….”

Kate nodded. “I know,” she said. The man took off his sunglasses and rubbed his eyes. They could only see the side of his face, but Kate stopped and stared.

“It can’t be!” she said. “What’s he doing here?”

“What do you mean?” Mike asked. “What’s who doing here? It’s the thief! We knew he was going to be here.”

Kate stood up. “Let’s go!” she said. She started running toward the thief.

“Are you crazy?” Mike asked. “We promised we’d wait for your mom!”

But Kate didn’t stop.

Mike jumped up and ran after her. He was just about to grab Kate when the man turned around.

His face broke into a big smile. He opened his arms wide.

Kate sprinted the rest of the way toward the man. At the last second, she flung out her arms and wrapped them around the man in a huge hug. He dropped his sunglasses and hugged her back.

“Dad!” Kate cried. “I can’t believe you’re here!”