Status Updates From The Mystery of Angelina Frood

[....] “The point is,” replied Thorndyke, “that when you are investigating a crime you are playing against the criminal. But if the criminal is unknown to you, you are playing against an unseen adversary. If you are visible to him he can watch your moves and reply to them. Obviously your policy is to keep out of sight and make your moves unseen. And remember that as long as you do not know who the criminal is, you do

8/10. I didn't predict all that was going on.