Singularity is almost invariably a clue. The more featureless and commonplace a crime is, the more difficult is it to bring it home.

This line is spoken by Sherlock Holmes in Arthur Conan Doyle’s early Holmes story “The Boscombe Valley Mystery.” Holmes is discussing his method with Dr. Watson as they travel to investigate the killing of Charles McCarthy near Boscombe Pool. The local police view the case as straightforward—pointing to McCarthy’s son as the obvious suspect—yet Holmes cautions that crimes which look ordinary and lack distinctive features can be harder to prove, because they offer fewer peculiar details to trace back to a perpetrator. The remark frames Holmes’s preference for anomalies and “odd” particulars as the most productive starting points for detection.

Holmes argues that what stands out—an unusual behavior, object, or circumstance—often functions as the best evidentiary handle. Singular details create a trail: they narrow possibilities, connect actors to actions, and resist innocent explanation. By contrast, a “featureless” crime blends into the background of everyday life; its elements are generic enough that many people could fit them, making attribution (“bringing it home” to a specific culprit) difficult. The quote also hints at a broader epistemic principle in detective fiction: knowledge advances not by cataloging the typical, but by interrogating the exception, since the exception exposes hidden structure and motive.