The Missing Blue Letter
The Murder of Roger AckroydThis flow follows Mrs. Ferrars’s letter from its arrival in the study to its disappearance and its role in identifying the murderer’s fear.
increasing
Bearing strength in each event
decreasing
A Message Sent

A Message Sent
A final instruction
Mrs. Ferrars writes to Ackroyd after their conversation and promises to name the blackmailer. She believes the truth should emerge after her death.
A dangerous document
The letter can expose the person who has been extorting her. Its arrival turns Ackroyd’s private grief into an immediate threat to the blackmailer.
The Letter Arrives

The Letter Arrives
Ackroyd recognizes the writing
The evening post brings a blue envelope in Mrs. Ferrars’s handwriting. Ackroyd reads the opening lines and realizes that she has left a message.
Sheppard urges disclosure
Sheppard presses him to read the letter immediately, especially the blackmailer’s name. Ackroyd refuses, unknowingly protecting the killer for a few more minutes.
The Missing Name

The Missing Name
An empty place on the table
The blue envelope is absent when police inspect the study. Sheppard says he noticed the loss, but cannot reliably establish when it disappeared.
Suspicion spreads
The missing letter suggests someone wanted to erase the blackmailer’s identity. Parker, Raymond, Blunt, and other people near the room become possible suspects.
A Letter as Motive

A Letter as Motive
Several explanations remain
The letter may have been taken by the murderer, removed by Parker, or destroyed by Ackroyd himself. Poirot does not assume its disappearance proves a single theory.
The threatened blackmailer
Its contents matter because the name could expose a long-running crime. The letter supplies a motive for murder, but must be interpreted alongside the doctor’s opportunity.
The Unread Letter’s Answer

The Unread Letter’s Answer
A name never needs to be read aloud
Sheppard’s conduct reveals that he feared what Mrs. Ferrars had written, even though Ackroyd never read the letter in his presence. His crime prevents its disclosure.
The evidence joins the pattern
The missing message, the blackmail payments, and Sheppard’s financial story converge. The letter’s absence becomes meaningful through the actions it provoked.
Thursday night, before Mrs. Ferrars dies
Friday evening, around eight forty
Friday night, after Ackroyd is killed
During Poirot’s investigation
Near the ending, after Poirot identifies Sheppard