On the orders of the famous detective Sherlock Holmes, Nick, Ella, and their dog Watson travel through space and time to complete missions and solve mystery cases. Along the way, Ella and Nick, as well as young readers, learn about the respective era or subject matter. Triple differentiation means: Each chapter offers all three reading levels, allowing the reader to decide after each chapter at which level they would like to continue the story. Each reading level tells the story from a different perspective: Ella's, Nick's, or Watson's. The reading levels are: - Level 1: short sentences, reduced vocabulary, large print, syllabication - Level 2: longer sentences, larger vocabulary, normal font size, no syllabication - Level 3: more complex sentences, including foreign words, larger text volume. At the end of each chapter, a summary is provided.