“‘My dear fellow,’ said Sherlock Holmes as we sat on either side of the fire in his lodgings at Baker Street, ‘life is infinitely stranger than anything which the mind of man could invent. We would not dare to conceive the things which are really mere commonplaces of existence.’”

The story’s opening sentence, as well as the setting established by Watson’s narration, establishes the protagonist as thoughtful, idiosyncratic, and prone to noticing the unnoticed. This manner of thinking is impressed upon the reader, too, as more strange details unfold. That these “dear fellows” talk like this by the fire conveys a sense of security in Holmes’s apartment and in his philosophy. Here where the truth of reason prevails, one is free to discourse about the nature of life; this is a safe place.

“Depend upon it, there is nothing so unnatural as the commonplace.”

“A Case of Identity” presents the lowest-scale criminal activity so far in the Holmes series (low-scale in terms of physical violence, legally actionable offenses, and number of people involved; not in terms of seriousness or individual depravity). Holmes’s comment is a teaser for the drama to unfold; readers this time will look at a more suburban situation, involving only three close-knit people, and this sentence hints that, though not as bizarre and sensational as a homicide, this case is no less “unnatural” or worthy of attention.