In The Elsinore Vanish Matt and Chess are presented with a variation of the classical locked-room mystery. This is the kind of thing where a body is found in a locked room, there is apparently no way the murderer could have been near the body to commit the crime and no way they could have escaped. The murder seems to defy logic.
Edgar Allen Poe’s story, “Murders in the Rue Morgue”, arguably the most well-known of the early murder mysteries, was a locked room mystery.
In The Elsinore Vanish it is not the dead person, but a jar of poison that was locked away.
The murder victim was a keen amateur magician, and while they are enquiring into what happened, Matt and Chess keep coming across another young conjurer, Paz, who shows them a card trick, The Elsinore Vanish. They think it is a bizarre distraction.
But the Elsinore Vanish is about the impossible.
In the end, it provides the key to the whole mystery.