None of the characters of The Fourth Deadly Sin is developed in depth. Each has his or her distinguishing traits which may or may not affect the investigation. For instance, Helen Venable is notable for her resentment toward men, who she believes steal credit for her work. Thus, she does not pass on important information to Delaney, delaying his solving the case. The main character Delaney has his own significant traits: a love of police work, an ability to strike just the right tone when interviewing suspects, a passion for his wife, and a love of sandwiches.

Descriptions of his bizarre sandwiches abound in the novel, and his relentless passion for them is probably meant to be endearing, but they have little to do with the plot. Even so, Sanders's powers of description make the sandwiches look very good.

Personalities are important to the progress of the plot...