Gaston, a curious and perceptive little boy, visits Vienna with his big sister Noemie and their parents. But it's impossible to attend the riding show at the Spanish school as the famous Lipizzaner horses have disappeared! Intrigued by what's happened, Gaston investigates.

Marie-Pierre Garnier offers children a fun and fascinating way to discover Vienna - the place she has adopted as her home. Through a riddle that uses her hero's powers of observation and deduction, children can join along for the adventure while also being provided with many anecdotes linked to the city's history.