It is fairly well know, at least to those interested in the history of the theory of natural selection, that Alfred Russel Wallace conceived this idea whilst suffering from fever in February 1858. When he had recovered sufficiently he wrote an essay about it, which he posted together with a covering letter to Charles Darwin probably in early March from Ternate Island in Indonesia. What few people realise is that Wallace's theory was conceived on the neghbouring island of Halmahera (which Wallace knew as Gilolo) and that the original essay and the covering letter mysteriously disappeared long ago. Historians do not know what Wallace wrote in the letter, and the disappearence of it and the envelope it and the essay were posted in have given rise to a conspiracy theory, which has been the subject of a number of books and research papers (see e.g. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1095-8312.2011.01858.x). Leaving the conspiracy aside, what do we know about the fate of the letter?