Who is Malone's only visitor during his time at the institution in the novel, Malone Dies?

The Anonymous Man is the only person to visit Malone at the institution. He has no name or identity, and the reader never finds out who he is or why he is Malone's keeper. The fact that he deals a "violent blow" (262) to Malone's head for seemingly no reason, and his failure to answer Malone's questions regarding why he is being kept (265), is a representation of Beckett's theme: the inscrutability of the reasons behind the circumstances that people fall into.