In one obvious sense this paper is a misfit within a book that otherwise charts so much achievement. The unfinished project that it describes occupied the attention of two Scottish professors and, in its later reincarnation, a distinguished German academic, himself subsequently a professor, for a total of thirty-six years. Publishing projects that come to nothing are often at least as interesting as those that come to fruition; they will never be able to claim significance, but they may instead provide mystery or perhaps a salutary lesson. I offer two excuses for unearthing the story of the Plato Lexicon. First, it is reasonably well documented; second, it illustrates a number of features about the history of classical scholarship and publishing in the nineteenth and twentieth centuries. Although in one sense the story is incomplete and remains a mystery, the answers to several important questions are clear enough: how and why the project came into being, how it was undertaken, and why it failed.