Q:  When I am referring to characters and events, need I mention which of the two films in which said character/event is featured? I will, of course, indicate in the essay that I am speaking about both “The Thirty-Nine Steps” and “The Lady Vanishes”, but must I always be writing things like: “Consider, for instance, the performance of Mr. Memory at the Music Hall in ‘The Thirty-Nine Steps’”, or can I assume sufficient familiarity with the films’ content on the part of the reader, and drop the “in The Thirty-Nine Steps”?

A: In terms of style and clarity, you should clarify the film the first time you mention a character, but you need not mention the film name every subsequent time you mention the character. There are exceptions, of course: if you are talking about one film for an extended period of time and then throw in something about the other film, it makes sense to highlight your change. Your basic aim is to make sure the reader can follow you, without repeating things unnecessarily!