Nils Jacket versus Agent X

Louis Dattaque, the renowned CEO of the arms company bearing his name, has just been found murdered in his office. How did the killer manage to commit the crime, given that the door was locked from the inside and the room is on the 9th floor? And above all, why did he take the trouble to draw a large X on the wall with his victim's blood? The best police officers in the country are on the case, but it is YOU, Nils Jacket, private detective, whom the firm hires to solve the crime. This is the first time an investigation of this magnitude has been entrusted to you. Will you rise to the challenge? Will you have what it takes to face Agent X, the most famous spy? This adventure does not involve luck in the form of dice. You must unmask Agent X through logic and deduction.