I think that is a big leap to make. Do we know that undergrounders immortal or do you make the assumption that because he was an undergrounder, then he couldn't have died on the island? Even if Napoleon did not die on the island of Saint Helena, it doesn't follow that the story about the doppelgangers therefore is true.So, if Napoleon was an underground man, then the legends that say he didn't die on the island of Saint Helena, but was actually the last of his four doppelgangers, are true.