Carolyn Wells opens In the Onyx Lobby with a quarrel over a "family feud" conducted by two women, voiced by Sir Herbert Binney in the ornate living room of the Campanile Apartment House. The building itself—with its onyx pillars, tessellated floor, and deeply embrasured windows—is established as both setting and silent witness. The lobby, lined with massive pillars, becomes the stage for a murder that occurs while the elevator is in use, a timing that the detectives later reconstruct with precision. Wells uses the architecture to create opportunities for concealment and sudden violence, grounding the mystery in physical space.

A Feud Framed by Architecture

The Campanile's onyx lobby is more than a backdrop; it is a mechanism of the plot. The murder takes place in the angle between a pillar and the wall, a spot that offers partial concealment. The elevator's operation dictates the murderer's window of opportunity: the stabbing occurs while the elevator carries a passenger upstairs. Wells repeatedly returns to the lobby's layout—the pillars, the lighting, the tessellated floor—as characters reconstruct the crime. The detectives note that the lobby is "so brightly lighted" that anyone outside could see inside, yet the pillars cast shadows. This tension between visibility and concealment drives the investigation.

The Missing Knife and Its Owner

A key piece of evidence is a knife owned by Miss Letitia Prall, which goes missing after the murder. The detectives seize on this: "Her ownership of the knife, and her making no effort to find it, though missing, are evidence enough for me," says Corson. Yet the narrative does not confirm her guilt. The knife could have been taken by others—the "little chorus chickens" or the chambermaids. Wells withholds certainty, letting the object circulate as a suspicion rather than a proof. The reader, like the detectives, must weigh ownership against opportunity.

Voices of Suspicion: The Interrogation Style

The dialogue in the excerpts reveals a layered investigation. Bob Moore, a reader of detective stories, is mocked by Gibbs: "those things are only for story-books,—such as you're eternally reading, Moore." Yet Moore's literary knowledge proves useful; he notes that criminals usually leave a trace. The exchanges among Moore, Corson, and Gibbs show a tension between practical police work and theoretical deduction. Corson builds a circumstantial case against Miss Prall, while Moore demands "some sort of evidence." This back-and-forth mirrors the reader's own process of sifting clues.

Movement Between Scenes: From Lobby to Library

The narrative moves fluidly between the lobby, the Prall apartment, and other rooms in the Campanile. Chapter titles like "The Library Set" and "The Little Dinner" indicate that the investigation unfolds through social gatherings as much as formal interviews. The murder is discussed in living rooms and hallways, with characters reconstructing movements: who was in the elevator, who could have waited in the shadows. Wells uses these shifts to keep the suspect pool open, never letting the reader settle on a single location or perspective.

Readers should attend to the way Wells uses the building's physical details—pillars, elevators, staircases—as both obstacles and aids to detection. The feud between the women is announced early but never fully explained in the excerpts; its motives remain tangled with the murder. The story rewards attention to timing and placement, as the solution likely hinges on who could have been where when the elevator moved.