I saw The London Eye Mystery by Siobhan Dowd and thought, "Yippee, a mid-grade mystery!" I picked it up eagerly, and was not disappointed. Though I didn't swallow it in one gulp, I came as close as I could.
Plot Summary: Ted and his older sister, Kat, receive a visit from their cousin, Salim, who is about to move from England to NYC with his mom. Salim has never ridden the Eye, a huge observation wheel in which people riding in sealed pods get a twenty-five mile view (on a clear day) of London in all directions. As the kids queue up to buy their tickets, a strange man approaches and almost forces a free ticket on Salim. Though somewhat nervous, Ted and Kat decide they'll save their money and that Salim should accept the free ticket since this may be his last chance to ride. The siblings track their cousin's pod as the Eye makes its thirty-minute revolution. The pod opens -- all the pods open -- and the riders emerge. No Salim. No Salim at all.
Besides the fact that this is a fine locked-room mystery, the characters are as strong as the plot. Ted has an unnamed "syndrome," which to this untrained eye sounds like mild autism or some relative thereof. His hands flap when he's nervous, and he has trouble with eye contact. He counts how many pieces of "shreddies" he eats for breakfast. He's obsessed with weather, though this is at least partly his passion for the science of meteorology. His brain runs "on a different operating system," as he puts it. His sister coaches him in the nuances of body language, and he has memorized a "five-point code" given to him by his neurologist for reading facial expressions, because that's the only way he can figure out people's feelings. Each time someone smiles, Ted reminds himself that this means "he and I could become friends." At certain moments, everyone laughs, and Ted says, "I didn't know what was funny but I laughed too." But -- after dismissing a number of wild theories such as his cousin spontaneously combusted --it's exactly Ted's "operating system" that helps him work out what happened to Salim.
Kat grows as a person, too. She starts the story obsessed with her Hair Flair catalogue, ditches school, and says things to Ted like, "Get stuffed, you creep," because Ted is incapable of not speaking the complete truth when his mouth opens. Yet she becomes Ted's full partner in solving the mystery of Salim's disappearance, playing the brave, action-packed role to his mastermind. She is the only one who will listen to Ted's ideas, as the adults keep brushing him off with, "Shush, Ted, now's not the time." And because she does listen, she becomes every bit as responsible for the last-minute victorious outcome as Ted. The way Ted sees it: "When I talk to people about something I've found out, they don't listen. When Kat does, everybody listens."
As the solution to the mystery unfolds, we discover that Salim's operating system is pretty clever as well. Throw in Salim's dramatic mom, Aunt Gloria; a few more run-ins with the mysterious ticket benefactor; and the police inspectors; and we have a cast of colorful, believable, enjoyable characters who illustrate a number of themes about Difference -- that two people who are very different just might be two halves of a whole; that some differences, such as transatlantic moves, may be harder to negotiate than we think; and that the "different" in "different operating systems" may well stand for "superior."