In The ABC Murders, we are introduced to Alexander Bonaparte Cust, a seemingly meek and unassuming man whose life takes a dark turn as he becomes embroiled in a series of chilling murders. The story unfolds in a British town where a string of murders occurs, each linked by the initials A, B, and C. Cust, who carries a railway timetable marked with those very letters, becomes an unlikely suspect due to his forgetfulness and peculiar behavior. The narrative begins with Cust at a public library, where he engages in a conversation with a librarian about a book he has been reading. His clumsiness and tendency to misplace his belongings, such as his briefcase, hint at deeper issues, including his struggles with headaches and a troubled past. As he interacts with other characters, including a fellow war veteran named Franklin Clark, the tension builds. Clark, who shares a bond with Cust over their war experiences, seems to take a particular interest in him, which only heightens the suspense surrounding Cust's character.