Dr. Armstrong's primary weakness is his firm belief that social class defines character and moral integrity. This conviction leads him to trust individuals based on their perceived status rather than their true nature.
The Nature of His Flaw
- Reliance on Social Standing: Dr. Armstrong holds a deep-seated belief that individuals of high social standing, wealth, or professional stature are inherently incapable of committing heinous acts such as murder.
- Misplaced Trust: This unwavering conviction makes him particularly susceptible to manipulation by those who present themselves as respectable or authoritative figures. He struggles to conceive of a person from an elevated social position as being a ruthless killer.
Exploitation and Consequences
This profound weakness is ultimately exploited by the true murderer, Justice Wargrave. Dr. Armstrong's inability to see through Wargrave's façade of respectability proves fatal:
- Assisting the Killer's Scheme: Due to his trust in Wargrave's high social standing, Armstrong is persuaded to assist Wargrave in faking his own death. This act is a pivotal part of the murderer's elaborate plan to deceive the other guests and orchestrate his own disappearance from suspicion.
- Fatal Encounter: Blinded by his class-based judgments, Armstrong willingly agrees to meet Wargrave out by the cliffs late at night. This isolated location provides the perfect opportunity for Wargrave to commit his final murder.
- Demise: With Armstrong's guard down and his trust fully invested in a man he deemed "above suspicion," Wargrave easily pushes him over the cliff, leading to Dr. Armstrong's death.
Dr. Armstrong's downfall is a direct result of his inherent bias, which prevents him from seeing the villainy hidden beneath a veneer of social respectability.
