Ema Vašková has always been extraordinary. The twelfth child in her family, born on the twelfth day, of the twelfth month as the clock struck twelve, she is fascinated by shadows and has a very particular skill for sneaking up on people - much to the bewilderment of her parents and siblings.
When Ema is sent to stay with her eccentric, bicycle-making Uncle in Prague, she meets Silvie - a girl just as extraordinary as Ema. Together they befriend bats, trawl treasures from the river and establish one firm rule: adventures are best served at midnight.
So when Silvie goes missing, Ema is determined to find her. Even if that means facing her darkest fears and infiltrating a very peculiar secret society known as The Midnight Guild . . .