En esta segunda entrega aparece la cuarta y última de las novelas: El valle del terror (1915) y el primero de los libros de relatos: Las aventuras de Sherlock Holmes (1892).
Since her father disappeared, she has received a large pearl through the post on the same day, every year, for six years. Who is sending them? And what about her father's paper with the words 'The Sign of Four' written on it? Sherlock Holmes alone can solve these mysteries.
