A subgenre of crime fiction is detective fiction, in which there is usually a detective character who solves the mystery. However, in some instances, there is no detective. In this essay, a comparative study is conducted using two clue-puzzles by Agatha Christie, one with a detective and one without a detective, to explore the detective’s function and the consequences of removing that function from the narrative. Among other theoretical concepts, a formula of the classical detective story with the pattern of action is used. By examining and comparing how the plots are structured and the types of narrators used in Christie’s A Murder is Announced and And Then There Were None, this essay argues that the presence or lack of a detective in a clue-puzzle will affect the reader’s experience of solving the crime, as well as describes how. A Murder is Announced follows the pattern of action, it has an omniscient narrator and sometimes insight into Miss Marple’s thoughts. And Then There Were None does not follow the pattern of action to the same extent, it has an omniscient narrator who often gives the reader access to characters’ thoughts, and sometimes employs a first-person point of view. The reader is guided by Miss Marple through the investigation and explanation in A Murder is Announced and can compare their solution with hers. In comparison, while reading And Then There Were None, the reader is alone without the help of a detective, which makes it more difficult for the reader to observe clues and figure out the solution to the crime. This essay’s contribution to the field is an analysis that explores the consequences of the presence or lack of a detective in a clue-puzzle, specifically focusing on the reader’s ability to solve the crime.