1“Help! A monster!” said Annie.

2“Yeah, sure,” said Jack. “A real monster in Frog Creek, Pennsylvania.”

3“Run, Jack!” said Annie. She ran up the road.

4Oh, brother.

5This is what he got for spending time with his seven-year-old sister.

6Annie loved pretend stuff. But Jack was eight and a half. He liked real things.

7“Watch out, Jack! The monster’s coming! Race you!”

8“No, thanks,” said Jack.

9Annie raced alone into the woods.

10Jack looked at the sky. The sun was about to set.

11“Come on, Annie! It’s time to go home!”

12But Annie had disappeared.

13Jack waited.

14No Annie.

15“Annie!” he shouted again.

16“Jack! Jack! Come here!”

17Jack groaned. “This better be good,” he said.

18Jack left the road and headed into the woods. The trees were lit with a golden late-afternoon light.

19“Come here!” called Annie.

20There she was. Standing under a tall oak tree.

21“Look,” she said. She was pointing at a rope ladder.

22The longest rope ladder Jack had ever seen.

23“Wow,” he whispered.

24The ladder went all the way up to the top of the tree.

25There—at the top—was a tree house. It was tucked between two branches.

26“That must be the highest tree house in the world,” said Annie.

27“Who built it?” asked Jack. “I’ve never seen it before.” “I don’t know. But I’m going up,” said Annie.

28“No. We don’t know who it belongs to,” said Jack.

29“Just for a teeny minute,” said Annie. She started up the ladder.

30“Annie, come back!”

31She kept climbing.

32Jack sighed. “Annie, it’s almost dark. We have to go home.” Annie disappeared inside the tree house.

33“An-nie!”

34Jack waited a moment. He was about to call again when Annie poked her head out of the tree house window.

35“Books!” she shouted.

36“What?”

37“It’s filled with books!”

38Oh, man! Jack loved books.

39He pushed his glasses into place. He gripped the sides of the rope ladder, and up he went.