by Blue Balliett
In this third installment from the author of Chasing Vermeer, Calder gets the opportunity to travel with his dad to Oxford, England. When he disappears into thin air, Calder's dad invites Tommy, Petra, and Mrs. Sharpe to come to England to help find him. Without Calder to keep the peace, Tommy and Petra must learn to get along so they can save their friend. This is a terrific adventure story that again combines elements of art, numbers, language and intrigue.