“The Case of ‘The Yellow Notebook’” contains reminiscences of Wittgenstein’s conversations with the philosopher Tatiana Gornshteyn (1904–80) on his visit to Leningrad in 1935. The reminiscences are contained in a document written by her daughter Ludmila. It records a story about a “Yellow Notebook” of his work (in the genre of his so-called Blue and Brown Books)—a notebook that, it is claimed, Wittgenstein gave to Tatiana and was subsequently lost. Attempts have been made to find it in Russia and all have failed. Biographical and historical context is provided in an introductory essay by the translator.