How Wargrave killed Mcarthur? I thought he just simply sneaked out and killed him when nobody watching? Nothing tricky AFAIK but lemme consult the book in case I'm missing something hehe. As for the revolver trick, I think he had some sort of elastic rope/cord attached to his glasses (you know those glasses with the normal 'tali' thing hehe, but instead he used a special cord). So he attached the revolver to that cord, (tied it to the trigger loop). Then the cord was stretched thru the door handle (one end of the cord that was tied to the the glasses, secured in place using his own weight-maybe by sitting/lying on it), and he hold the other end of the cord i.e the revolver. He used handkerchief to camouflage his fingerprints on the revolver.

So what happen was, he pulled the trigger (shot to his head) thereby releasing the revolver, and the elastic cord made the revolver 'thrown' to the door (coz of the door handle). Loosing the stretch, the elastic cord will look the same as normal glasses cord .