At Elysian Hall, a great exhibition space in post-War London, a cast has been assembled for a Medieval pageant show. There are knights in coloured armour, real horses, and a fair damsel in the tower on high. Tragedy is in the air when several members of the troupe are sent death threats before the show, and the worst comes to pass when one of the players is found dead killed during the performance while all entrances to backstage were observed and with the eyes of the audience on the other side. Inspector Cockrill and Inspector Charlesworth adopt the case, rivals in a race to answer the impossible question: how could it have been done?

First published in 1948, Brand's masterpiece of the impossible crime subgenre is a fiendishly complex yet riveting mystery, featuring nuanced characters, Shakespearean plotting, dumbfounding acts of misdirection and a truly thrilling denouement.