Writing realistic historical fiction—and especially screenplays—must be one of the hardest jobs in the world. You can spend your life studying the habits, language, and mores of people at a certain time and place, and no matter how much you know, you won't know everything, and there will always be somebody in the audience who knows something you don't, or who notices something you think no one will notice.

You can try to stick to the original, if there is one, but suppose the author says something like "Mr. Watkins paid us a visit, and told us that his mother had died."—and suppose the death of Mrs. Watkins is an important plot point that you can't simply omit. If you're going to turn that into a scene in a film, you've got to put some actual words into the mouth of Mr. Watkins, and some appropriate replies into the mouths of others. Woe betide you if you use some words or phrases that strike someone else as false or inappropriate to the period or setting.

Then, too, someone will have to decide how Mr. Watkins will be dressed, what the furniture will look like, whether Mr. Watkins will arrive on foot, or on a horse, or in a carriage, etc. All these are potential pitfalls.

Case in point: the movie Titanic. On the whole, it was a very well-researched movie, yet it has perhaps the longest list of "goofs" of any film, because hundreds of amateur history buffs have analyzed the film in great detail.

Will Fly: The error about "masochism" would have been caught by my hypothetical "anachronism checker"—that is, a modified spell-checker that uses a historically appropriate dictionary.