Using the split-page format, the reader must work through the exhibition, room by room, painting by painting. Each work in the anniversary exhibition contains details taken from two, three, four or five pictures in the gallery's permanent collection of modern art masterpieces. The details could be anything - a dog's head, a totem pole or a staring eye, for example. By carefully comparing each painting in the exhibition with photographs of the works in the permanent collection, readers must match each detail to the original work from which it is taken. If their powers of deduction are up to scratch, they will be able to work out who poainted each picture in time for new information panels to be made, as well as uncover the rogue painting so that it can be removed before the exhibition opens.