Sherlock Holmes is off on a new mission

“Mediocrity knows nothing higher than itself; but talent instantly recognizes genius.” - Arthur Conan Doyle, The Valley of Fear

Sherlock Holmes and Professor Watson are warned that someone named John Douglas is in grave danger and could be murdered at any time. The unfortunate event happens before Holmes can stop it and now he has to solve yet another daunting crime. He arrives at the crime scene - an old manor with a moat and a drawbridge - but very few pieces fall into place. For example, how did the murderer get inside?