Jack and Annie had had a same dream about Morgan. Having the same dream must mean something, they thought. They ran and climbed up into the tree house. She was waiting for them there.
She was in trouble, so had not any time to collect books for Camelot's library. To gather books through time, Jack and Annie must be Master Librarian. To be Master Librarian, they had to pass a test of solving four riddles.
The first riddle was something that is as rough and gray as rock, as plain as it can be. But it was hidden deep inside and there was great beauty in it.
They, in the tree house, landed on a coral reef, but it wasn't in a tree, builded of a stack of coral skeletons.
There they found a mini-sub which was tiny and had two seats facing the big window. Sometimes oceanographers took it on their travel to study the ocean floor. Even though Jack told Annie not to touch anything inside, Annie just pressed a few keys of computer in front of the seats. The mini-sub slid off the reef and dove silently down into the deep as soon as Annie did that.
Outside the glass was a strange world of bright moving color while sinking. The mini-sub was moving past colorful corals, and fishes of every color and size. Their book says there are 5,000 different species of fish and clam in tropical waters.
When two dolphins named Sukie and Sam were peering in the window, Jack and Annie looked up them. For a while all of them was like talking to each other as if they were friends.
After the dolphins swam off, they wanted to check the computer to find the answer of the riddle. When they pressed 'the book picture' on it, 'ship's log' flashed onto the screen. That was just trip of last week. They knew from log that the sub were defective, waiting to be taken away by helicopter to junkyard.
They really would have to get back immediately, but an octopus hugged the sub. As its suckers stuck to the window, the sub stopped. Then water dripped from cracks of ceiling, but Jack and Annie could not never get rid of octopus, before a hammerhead shark appeared. The octopus shot a cloud of black liquid into the water and disappeared.
When the shark swam behind a coral, more water was coming and spurting from ceiling, and rising from the bottom of the sub as well. It was not working to the reef in the distance, as the screen of it went blank.
They would have to swim to the reef without splashing because of the shark. As shark was heading toward them, zigzagging through the water, they both swam as fast and calmly as they could. It took forever for the tree house to get just a little closer. Just then, the dolphins appeared and helped to pull them toward the reef.
After Jack and Annie said good bye to the dolphins at the reef, they almost gave up their mission of finding the answer to the riddle. But, Annie stepped on something with her bare foot. It was rough and gray as a rock, and plain as plain can be. Oyster! Their book says, inside some oysters has a pearl, and its natural beauty makes it a treasure.
Finally, they climbed through the window of the three house, they stared at the scroll and in its place a word, OYSTER, instead of riddle.
They came back to the woods. No time at all had passed since they had left.
On their way home, they thought that the dolphins were the true pearl in the oyster, because it made up for everything. Soon Jack and Annie missed Sukie and Sam.
