One of the key properties of detective fiction is that readers are manipulated to believe wrong accounts of events to prevent them from guessing the solutions to crimes. This chapter examines plot manipulations in selected detective stories by Agatha Christie, studying reliability and unreliability in relation to how information is primed for believability. The chapter shows how explicit statements are used to construct characters as credible, positioning their accounts of the crime as reliable and, conversely, how statements may challenge characters’ credibility, making their accounts seem unreliable. Since the overall aim of detective fiction is to deceive the readers, these stories frequently include surprise reversals where characters who were previously presented as reliable are revealed as unreliable, and vice versa. The main aim of this chapter is to look at how reliability and unreliability are constructed in relation to a range of characters, particularly witnesses giving evidence, and the author’s manipulative strategies are observed in various stylistic modes, such as speech and thought.