Dr. Edward George Armstrong is one of ten people summoned to Indian Island by Lawrence Wargrave in Agatha Christie's novel 'And Then There Were None,' who have committed murder in a way that the law cannot prove or punish them for. Some twenty years before the events of the novel, Armstrong operated on a woman while drunk, resulting in the patient's death. He used the hospital management to cover up his crime, though the nun who accompanied the patient later confided his crime to Wargrave.
On Indian Island, Wargrave enlists his help in faking his death by playing on his suspicion of Philip Lombard as the murderer. He convinces the doctor to help him expose Lombard by pretending to be a victim. They cause a distraction, and Wargrave poses as a dead man. The doctor pronounces his death, and because of his profession, no one contradicts him.
That night, Wargrave takes the Doctor walking on the sea cliffs to discuss the next part of the plan, and pushes Armstrong over the cliff to his death. He later washes up on the shore and is found by Philip Lombard and Vera Claythorne.
Armstrong's death corresponds to the 'Ten Little Indians Rhyme,' "A red herring swallowed one and then there were three" in two ways: First, his mode of death by drowning, second, a 'Red Herring' refers to a false trail or deception, which Wargrave used to trick him into following him.