“You want to what?” Marly’s mom leaned back in her desk chair, her eyes fixed on Marly and her friends. “No. Absolutely not. You are not going to wander around inside Mr. Summerling’s house by yourselves.”

Marly half expected this. “But he wants us to. See?” She showed her mother the letter Ms. Lovelace had given them, then held her breath while Mom read it to herself.

Isla and Sai shuffled their feet and avoided looking at Marly’s mom. They all knew that if they could get one parent to agree to this, the others would probably agree, too.

“I don’t know, honey . . .” Mom handed the letter back to Marly.

“You always said Mr. Summerling was quirky,” Marly said. “You said he was quirky, but nice. This is just another example of him being quirky!”

Mom tilted her head. That meant she was thinking about it.

“Please, Mom,” Marly begged.

“Please, Mrs. Deaver!” Isla and Sai chimed in.

Mom sighed. “Why don’t you all get yourselves a snack while I talk to the other parents and see what they think,” she said, reaching for the phone on her desk.

The kids went into the kitchen, and Marly got everyone cartons of yogurt. They ate standing up.

“Our parents are never going to let us do this,” Isla said.

“They might,” Sai said.

Marly didn’t say anything. But now that they knew there was more treasure to be found, their parents had to let them search. They just had to!

As they were finishing their yogurt, Marly’s mom came in. “Two hours,” she said. “I want you all back here in two hours. And be respectful while you’re there.”

The kids all jumped up and slapped high fives.

“Thanks, Mom!” Marly gave her mom a hug. Then she and her friends trooped next door.

A tall hedge and black wrought iron fence surrounded Mr. Summerling’s property. There were old appliances, tires, and other junk scattered around the overgrown yard. The faded yellow house had a wide front porch and a tall square tower that stuck up above the trees.

They huddled around the locked gate out front. When Mr. Summerling lived here, this gate was never even closed, much less locked. But it was now. Marly dug the little key out of her tote bag and slipped it into the slot at the bottom. The lock clicked open.

“Have either of you ever been inside Mr. Summerling’s house?” Sai asked as they started up the front walk.

“No.” Isla shook her head.

Marly hadn’t been, either. But she’d always wondered what it was like inside. Especially that tower room.

“I wonder what’s going to happen to Mr. Summerling’s house now that he’s . . . you know . . .” Isla couldn’t say that last word out loud.

Marly remembered how Jay Summerling had asked Ms. Lovelace about the house in her office that day. Jay had assumed the house was his, but Ms. Lovelace wasn’t sure about that. She had other letters from Mr. Summerling, but she refused to open them. She said she had instructions for when each one was to be opened, and she was going to follow those instructions.

“Do you guys think Mr. Summerling is really dead?” Sai asked suddenly.

“What?” Marly asked, shocked.

“Of course he is,” Isla said. “That’s why Ms. Lovelace read his will.”

“I don’t know,” Sai said as he clomped up the porch stairs. “His body was never found. And think about the treasure hunt we just finished. When would Mr. Summerling have set it all up? Right before he left for this last treasure hunting trip? Why would he do that? He couldn’t have known he wasn’t ever coming back.”

Marly stopped halfway up the steps. She hadn’t thought about any of that before.

“Ms. Lovelace probably set it up,” Isla said. “Mr. Summerling probably left directions for what to do.”

“But when we started the treasure hunt, Ms. Lovelace told us and our parents that she didn’t know what was at the end of it, remember?” Marly said. “So how could she have hidden that last note in the tree house?”

“Right?” Sai said, obviously happy to have Marly on his side.

Isla looked a little pale. “Well, where has Mr. Summerling been all this time if he’s not dead?”

“Maybe in there.” Sai gestured toward the house. “Maybe he’s waiting for us to come in right now!”

Isla’s face grew even paler as Sai walked over to the door and turned the knob. “It’s locked.” He frowned.

“Well, I don’t think we need a key,” Marly said, pressing closer. “See? It’s got an electronic keypad. What we need is the combination, like the lock at the tree house.”

But unlike the lock at the tree house, this combination required letters, not numbers.

“We could also try ringing the doorbell,” Isla said. She pushed the button and a doorbell chimed like a grandfather clock somewhere deep inside the house. They tried to peer through the front windows, but dark shades blocked their view.

No one came to the door.

“Maybe the combination is hidden in the new letter,” Isla suggested. “You know, like the words make a T were hidden in that other letter.”

Marly pulled the letter out of her bag and they all put their heads together, which knocked Isla’s headband to the ground. She bent to pick it up.

“I don’t see anything weird with any of the words or letters in this letter,” Marly said.

“I can’t believe we’re stuck already,” Sai grumbled. He started pacing back and forth on the porch.

“Wait, that’s it!” Isla pointed to the word stuck in the new letter. “‘If you ever find yourselves—’”

“‘—stuck,’” Marly read along with her, “‘remember who you are. That will always get you through!’”

Sai turned. “Through the door?” He let out a short laugh. “Good one, Mr. S! So, who are we? Sai, Marly, and Isla. But who knows what order he programmed our names?”

“I don’t think the combination is our names,” Marly said. “Look at the beginning of the letter. ‘Dear—’”

“‘Treasure Troop,’” Isla said.

“Ah,” Sai said. He stepped up to the keypad and pressed T . . . R . . . E . . . A . . . S . . . U . . . R—

It buzzed on the R and a red X appeared in the corner of the keypad.

“That’s not right?” Marly said with surprise.

“Maybe you missed a letter,” Isla said. “Try it again.”

Sai pressed T . . . R . . . E . . . A . . . S . . . U . . . R—

Bzzzzzt!

“Argh!” Sai stomped his foot. He tried one more time. T . . . R . . . E . . . A . . . S . . . U . . . R—

Bzzzzzt!

“Okay, stop.” Marly put her hand on Sai’s shoulder. “That’s obviously not right.”

“Go ahead and try our names,” Isla suggested.

Sai tried S . . . A . . . I . . . M . . . A . . . R . . . L—

Bzzzzzt!

And S . . . A . . . I . . . I . . . S . . . L . . . A—

Bzzzzzt!

And I . . . S . . . L . . . A . . . S . . . A . . . I—

Bzzzzzt!

“Wait,” Marly said. “It always buzzes after you press a certain number of letters.”

“Hey, you’re right,” Isla said. “How many?” She counted on her fingers while Sai pressed M . . . A . . . R . . . L . . . Y . . . S . . . A—

Bzzzzzt!

“Seven,” Sai said. “So, what’s a seven-letter word that says what we are?”

“Oh, I know!” Marly said with a grin. “Let me try.”

Sai stepped aside and Marly pressed F . . . R . . . I . . . E . . . N . . . D . . . S.

A green check mark appeared on the keypad and the door unlocked.