A stolen painting. A series of unexpected events. Two smart children. Petra and Calder live in a neighbourhood where strange things have started to happen. Seemingly unrelated events connect, a sharp old woman seeks their company - and a priceless Vermeer painting disappears. Before they know it, the two children are drawn into an international art sensation where no one is above suspicion. They must rely on their intelligence and a newly acquired knowledge of the artist Vermeer to crack an art crime that has left everyone baffled.