Dear Mr. Henshaw Diary 46-51 Summary

Leigh runs out of room in his first journal and starts a second.
He also buys a beat-up black lunchbox like men carry, which is totally different from the cartoon kind.
The thief strikes again, but Leigh isn't too upset because he's got a plan.
The library has some easy books on batteries and electricity that Leigh studies.
He gives up on the wax man story and tries to write a poem about butterflies, but images of batteries keep dancing in his head.

The butterfly poem he's trying to write isn't working out.
Neither is writing his dad a thank-you letter for the $20, though he's not sure why he can't finish it.

Armed with his lunchbox and $20, Leigh goes to the hardware store.
A nice old guy who works there helps him find the right pieces and gives him advice about building an alarm.
Leigh likes the way the old guy calls him "son" and wishes his dad wouldn't call him "kid."
Once at home, he arranges, hooks, and wraps all the pieces together into his lunchbox, and eureka—it works.
It works so well that his mom comes in to find out what all the racket is about. She helps him figure out where in the box his lunch can fit.

It's an exciting day for Leigh. He and his mom carefully pack the working lunchbox, he waits all morning on the edge of his seat for it to go off, and…nothing happens.
Now it's lunchtime, and Leigh is not sure what to do. If he opens his lunch, the alarm will go off.
But he's hungry, so what's a guy to do?
The alarm goes off, startling everyone, and suddenly everyone is noticing him: teachers, the principal, the kids with boring lunches (like Barry), and other kids who've had things stolen just like Leigh.

One of the kids in Leigh's class, Barry, asks him to come over after school to help put an alarm on his door.
Barry doesn't have the right battery for the job so they mess around with his models instead.
Leigh still doesn't have a good idea for the Young Writers contest, but he's feeling so good about hanging out with Barry that he writes the thank-you note to his dad.

Lots of kids show up with alarmed lunchboxes, and the cafeteria is really loud for a while.
The fad fades away, and even Leigh stops setting his alarm.
The thief stops stealing his good stuff.
He doesn't find out who the thief is, but he discovers he's glad he doesn't know.
He doesn't want the kid to get into trouble now; maybe he came to school with a crappy lunch or no lunch at all.