Heatwave

Summer has settled over Odyssey and refused to leave. The air is thick, the sidewalks shimmer, and nobody can think of a single thing to do. On the front porch that doubles as his detective office, Jack Davis sits with his sidekick Oscar, trading the same question back and forth until it wears out: what do you want to do?

Then the answer walks right past them. A boy they do not know comes down the street, whistling, carrying a knapsack and an armload of lumber. He has been doing it every day for at least a week, always heading toward the woods. To Oscar, that is somebody else's business. To Jack, wearing a trench coat in hundred-degree weather, it is a case.

The trail starts badly. Jack leads Oscar into the woods on the strength of what he calls sheer cunning, a keen sense of direction, and his experience in the Boy Scouts, and hours later the only thing they have found is how lost two boys can get. But Jack reasons it out. Lumber has to come from somewhere, and somewhere in Odyssey means Mr. Watson's hardware store. Mr. Watson confirms the mystery kid buys wood almost every day and pays cash, so there is no name on any account. He also passes along one strange word the boy let slip. Whatever he is building, he calls it Wonder World. Then Mr. Watson offers some advice Jack does not much want: do not go poking your nose where it does not belong, and do not let your imagination run away with you.

At Whit's End, Robyn Jacobs supplies the missing piece. The mystery kid uses Mr. Whittaker's library, and anyone who borrows a book has to sign the checkout card. Among the familiar names is one that is not a name at all, just the initials DD, written beside a book called A Guide to Learning Through Your Imagination by John Avery Whittaker. Jack decides that thinking time is over. What the case needs now is action.

The next morning Jack and Oscar stake out the hardware store with Oscar's father's walkie-talkies, then shadow the boy deep into the humid woods. Along the way they hear him fighting a sword duel with an enemy who is not there, using nothing but a tree branch, and Oscar begins to wonder whether following a stranger this far was ever a good idea. Moments later the ground gives way and Oscar lands in a shallow pit, his walkie-talkie cracked underneath him, while the mystery kid announces that the intruders have fallen into the moat of his great fortress.

The moat is a hole. The fortress is imaginary. The boy is Digger Digwillow, and he is only playing pretend - something the two detectives are slow to catch on to. He has seen Jack and Oscar around Whit's End plenty of times, and he tells them he would have explained everything if they had simply asked. Mr. Whittaker has been teaching him that there is a right way and a wrong way to use an imagination. The wrong way lets it run off with you and land you in trouble. The right way uses it to build things, learn real ideas, and help people. Digger has ridden the Imagination Station into a story from the Bible and met Jesus there, and the experience left him wanting a place of his own where that kind of wonder could keep going.

Then he tells them to look up. Wonder World is a treehouse. Jack, who has spent days imagining a secret worth solving, stares at plain wood and nails and feels the case deflate. Digger sees something else entirely, and says so: Noah's ark riding out the flood, a castle in the Middle Ages, a cabin in the wilderness, a headquarters for secret agents, any place at all where good fights evil and wins. He keeps to himself, he admits, because most kids look at a tree fort and see only lumber, and he would rather have friends who see more.

Oscar sees a hideout from enemy soldiers. Jack looks again, harder, and finds the hut Robinson Crusoe built on his deserted island. With that, Digger welcomes them both to Wonder World, and the three of them race for the top - though Jack stays behind for one small piece of detective business first. He has decided the trench coat is only going to get in the way.