1"It's still here," said Jack.

2"It looks empty," said Annie.

3Jack and his seven-year-old sister gazed up at a very tall oak tree. At the top of the tree was a tree house.

4Late-morning sunlight lit the woods. It was almost time for lunch.

5"Shhh!" said Jack. "What was that noise?"

6"What noise?"

7"I heard a noise," Jack said. He looked around. "It sounded like someone coughing."

8"I didn't hear anything," said Annie. "Come on. Let's go up."

9She grabbed onto the rope ladder and started climbing.

10Jack tiptoed over to a clump of bushes. He pushed aside a small branch.

11"Hello?" he said. "Anybody there?"

12There was no answer.

13"Come on!" Annie called down. "The tree house looks the same as it did yesterday."

14Jack still felt that someone was nearby. Could it be the person who'd put all the books in the tree house?

15"Ja-ack!" called Annie.

16Jack gazed over the top of the bushes.

17Was the mysterious M person watching him now? The person whose name began with M?

18Maybe M wanted the gold medallion back. The one Jack had found on their dinosaur adventure. Maybe M wanted the leather bookmark back - The one from the castle book.

19There was an M on the medallion. And an M on the bookmark. But what did M stand for?

20"Tomorrow I'll bring everything back," Jack said loudly.

21A breeze swept through the woods. The leaves rattled.

22"Come on!" called Annie.

23Jack went back to the big oak tree. He grabbed onto the rope ladder and climbed up.

24At the top he crawled through a hole in the wooden floor. He tossed down his backpack and pushed his glasses into place.

25"Hmmm. Which book is it going to be today?" said Annie.

26She was looking at the books scattered around the tree house.

27Annie picked up the book about castles.

28"Hey, this isn't wet anymore," she said.

29"Let me see."

30Jack took the book from her. He was amazed. It looked fine. Yesterday it had gotten soaked in a castle moat.

31The castle book had taken Jack and Annie back to the time of knights.

32Jack silently thanked the mysterious knight who had rescued them.

33"Watch out!" warned Annie.

34She waved a dinosaur book in Jack's face.

35"Put that away," said Jack.

36The day before yesterday the dinosaur book had taken them to the time of dinosaurs.

37Jack silently thanked the Pteranodon who had saved him from a Tyrannosaurus rex.

38Annie put the dinosaur book back with the other books. Then she gasped.

39"Wow," she whispered. "Look at this."

40She held up a book about ancient Egypt.

41Jack caught his breath. He took the book from her. A green silk bookmark stuck out of it.

42Jack turned to the page with the bookmark. There was a picture of a pyramid.

43Going toward the pyramid was a long parade. Four huge cows with horns were pulling a sled. On the sled was a long gold box. Many Egyptians were walking behind the sled. At the end of the parade was a sleek black cat.

44"Let's go there," whispered Annie. "Now."

45"Wait," said Jack. He wanted to study the book a bit more.

46"Pyramids, Jack," said Annie. "You love pyramids."

47It was true. Pyramids were high on his list of favorite things. After knights. But before dinosaurs. Way before dinosaurs.

48He didn't have to worry about being eaten by a pyramid.

49"Okay," he said. "But hold the Pennsylvania book. In case we want to come right back here."

50Annie found the book with the picture of their hometown in it. Frog Creek, Pennsylvania.

51Then Jack pointed to the pyramid picture in the Egypt book. He cleared his throat and said, "I wish we could go to this place."

52"Meow!"

53"What was that?" Jack looked out the tree house window.

54A black cat was perched on a branch. Right outside the window. The cat was staring at Jack and Annie.

55It was the strangest cat Jack had ever seen. He was very sleek and dark. With bright yellow eyes. And a wide gold collar.

56"It's the cat in the Egypt book," whispered Annie.

57Just then the wind started to blow. The leaves began to shake.

58"Here we go!" cried Annie.

59The wind whistled louder. The leaves shook harder.

60Jack closed his eyes as the tree house started to spin.

61It spun faster and faster! And faster!

62Suddenly everything was still.

63Absolutely still.

64Not a sound. Not a whisper.

65Jack opened his eyes.

66Hot bright sunlight nearly blinded him.

67"Me-ow!"