A stolen painting.
A series of unexpected events.
Two smart children.

Petra and Calder live in a neighbourhood where strange things seem to have started to happen. Seemingly unrelated events connect, an eccentric old woman seeks their company - and a priceless Vermeer painting disappears.

Before they know it, the two children are caught up in an international art sensation where no one is above suspicion. As puzzling clues draw Petra and Calder deeper into the mystery, they must rely on their intelligence, their powers of deduction, and a newly acquired knowledge of the artist Vermeer to crack an art crime that has left everyone baffled.