Watson, as the first-person narrator, relates the events of The Sign of Four in a suspenseful, urgent tone. As the novel unfolds, the mysteries—of Captain Morstan's disappearance, of Bartholomew Sholto's murder, and of the Agra treasure itself—only deepen. As Watson draws the reader further into his tale, Watson ensures that a constant sprinkling of subtle clues and Holmes's own observations will set the reader on edge. It's never quite clear what details will prove critical to unraveling the mystery until Holmes arrives at a new revelation. Doyle also makes ample use of sinister, suspenseful descriptions of characters and settings in order to sustain his ominous tone, as with Pondicherry Lodge:
Pondicherry Lodge stood in its own grounds and was girt round with a very high stone wall topped with broken glass. A single narrow iron-clamped door formed the only means of entrance. On this our guide knocked with a peculiar postman-like rat-tat.
No gothic novel would be complete without a dark and foreboding manor, and Doyle is not immune to using the conventions of the genre to sustain the book's sinister tone. By highlighting the murky, mysterious nature of each new setting in which Holmes and Watson finds themselves, Doyle ensures that the reader is always one step behind the legendary duo—which enhances the urgency of the novel's tone and ensures that the reader keeps the pages turning.
