A murder in the middle of a bourgeois party, many suspects and a single culprit that Inspector Requesens will try to discover. Barcelona, 1909. During a sumptuous ball of m ascaras at the Liceo, Victoria, Countess of Cardona, is murdered. He has a fatal wound on his head and on his hand a very valuable ruby that disappeared some time ago. It does not ser to the only death in the Great Theatre.