If you have any interest in Mary Shelley’s Frankenstein or vampires or Romantic poets or, who knows, Swiss tourism, you've most likely read Polidori’s name. He’s a curio, Polly Dolly, most notable not for what he wrote but for being nearby when other people wrote things. It’s a strange afterlife; to think you've landed a leading role, and then there you are, on stage, sure, and with big names too, but fixed to a mark far upstage and over to the left, near the wings, in the half-dark where the spotlight doesn't quite reach. “Poor Polidori.” That’s how Mary Shelley referred to him, writing years later. And he was. Here is how he creeps into letters, like this one written by Byron: “Dr. Polidori is not here, but at Diodati, left behind in hospital with a sprained ankle, which he acquired in tumbling from a wall—he can’t jump.” It was John Polidori’s misfortune to be comic without having a sense of humor, to wish to be a great writer but to be a terrible one, to be unusually bright but surrounded for one summer by people who were titanically brighter, and to have just enough of an awareness of all of this to make him perpetually uneasy. Also, he couldn't jump. Poor Polidori.