The Big Clock is a detective story with a twist: the detective is both the seeker and the quarry. George Stroud, a writer for Crimeways magazine, inadvertently becomes a witness to suspicious circumstances that lead him to believe his boss, the owner of the magazine and a publishing empire, may be guilty of murder. Rather than a “whodunit” in which the detective finds out the murderer’s identity, the plot of this novel revolves around George’s dual roles. The boss, Earl Janoth, hires Stroud to find out who this potential witness is. The reader comes to suspect that Janoth already knows the witness is Stroud. Because George was not actually in the room where the murder took place but was standing outside the building, he did not see the crime committed.

In a complex narrative structure that makes Stroud the protagonist, as his perspective dominates most of the chapters, Kenneth Fearing also puts other characters in prominent positions in different chapters. This method gives the reader insights that George lacks about the case.

Both Stroud and Janoth are married. Janoth has been having an affair with Pauline Delos, whom Stroud meets at a party Janoth is hosting. Stroud also begins an affair with Pauline, a tempestuous blonde. One night, when he drops her off at home, he sees Janoth meet her outside and go up to her apartment with her. Janoth sees a shadowy figure on the street, interrogates Pauline about him, and strikes her in a rage. The next day, it is revealed that she was killed. The plot twist comes when Janoth hires George head up a team of investigators to find the shadowy figure. Because George assumes his boss is the killer and that he will try to frame the other man, he is intent on escaping detection.

As the investigation traces Pauline’s final days over the preceding weekend, witnesses are located at shops and bars where they had gone together. Stroud feels the web closing around him. All these witnesses gather at the Janoth Enterprises headquarters, having seen the shadow man enter. Stroud is saved at the last minute, as Janoth apparently jumps to his death, possibly despondent over a corporate takeover in which he has lost his business. But the reader is left to wonder: Was he pushed?