"Hey!" Nathan yelled, rushing after Nora as she tiptoed across their yard.
"What are you doing? Why'd you climb out that window?"
"Come on," Henry said to Cole and Maggie. "Let's catch up to them."
The Lemonade Detectives ran across the yard after Nathan.
By the time they reached him, Nora had stopped and spun around.
She glared at her brother.
"It's none of your business!" she yelled at him.
"Where were you going?" Cole asked Nora, glancing around the yard.
Henry looked around too. Nathan and Nora's backyard was really nice.
There was a big maple tree in the middle where Nathan and his dad had built a tree house.
On the left there was a short picket fence between their yard and the one next door.
A tall hedge on the right blocked the view of the other neighbors' house.
There were no neighbors at all at the back of the yard, just a thick forest.
Henry was pretty sure Nora was headed there when they'd caught her.
"Yeah," he said. "Where were you going, Nora?"
Nora stared at Henry, then at each of the others.
She looked suspicious. "Who wants to know?"
"The Lemonade Detectives, that's who," Maggie replied.
"We want to know what you're up to!"
Henry winced. He didn't think it was a very good idea to tell Nora that they were investigating her.
But Maggie was impulsive. She often spoke before she thought.
Nora stared at them all again. For a second she didn't answer.
"Well?" Nathan demanded.
"I was just walking across the backyard," Nora said at last.
"What's wrong with that?"
"Why did you climb out the playroom window instead of using the door?"
Nathan pointed to the back door of their house. "It's right there, you know!"
"I was in a hurry," Nora said.
"I, um, saw a butterfly and I wanted to catch it."
Henry glanced at Cole.
He could tell his friend was thinking the same thing he was. Nora was lying.
But how were they supposed to get her to tell the truth now?
She knew they were watching her.
That was going to make their job as detectives much harder.
"It's okay, Nora," Henry said. "Go ahead and do whatever you were doing."
"I wasn't doing anything," Nora said.
"I was just about to go back inside."
She ran over and climbed back inside through the window.
Maggie stared after her.
"You were right," she told Nathan. "She is acting even weirder than usual."
Cole shrugged. "So what do we do now?
She didn't seem very eager to tell us anything."
"We'll have to figure out what's going on in a different way," Henry said.
"Maybe we should try a stakeout," Maggie suggested.
"That worked last time we were suspicious of her."
"No it didn't," Cole said.
"Last time we staked out Nora's house, she turned out to be innocent."
"True, but Maggie's right," Henry said.
"If we hide and wait for Nora to sneak out again, we'll be able to follow her.
Then we can see where she's going and what she's doing."
"You mean we have to sit around here all day?"
Maggie suddenly didn't look very happy about the stakeout idea.
"What about my lemonade stand?"
Henry glanced at Nathan. "You said she's been sneaking out at night, right?"
"Sort of," Nathan said.
"Her bedtime is at seven, so it's not usually very late when she sneaks out."
"Perfect." Henry smiled. "All we have to do is come back at seven and wait!"
That evening at exactly seven o'clock, The Lemonade Detectives met behind the hedge along Nora's yard.
Nathan was waiting for them there.
"Perfect timing," he whispered. "Nora just went to bed."
Henry nodded. He peeked through the hedge.
It hid them from view, but allowed them to see Nora's house.
"Does she usually sneak out the back door?" he asked.
"She used to," Nathan replied.
"But Mom and Dad started locking it once all this started."
"Maybe she'll climb out the playroom window again," Cole said.
Nathan nodded. "Or she might use her bedroom window," he said.
"It's upstairs, but she knows how to climb down the house.
It's part of our family's fire-safety plan."
"Okay, let's watch both windows," Henry said.
They all settled down behind the hedge to wait.
But they didn't have to wait very long.
About twenty minutes later, they heard a window slide open.
Maggie peeked through the hedge. "It's Nora!" she whispered.
"She's climbing out her bedroom window."
Henry looked too.
He saw Nora climb out her bedroom window and jump to the ground.
She glanced around, and then scurried across the yard.
"She sure doesn't look like she's sleepwalking," Henry whispered.
"Come on, let's follow her!"