Throughout the novel, Dr.Armstrong is often the one to declare a guest's death. First Anthony Marston's, then Mrs. Rogers. He found General MacArthur dead, and declared Emily Brent dead. Wargrave discusses his "plan" with Armstrong in secret, saying that if Wargrave faked his death, the killer could incriminate themselves. Wargrave pretends to be shot, Armstrong declares him dead. This ends in his own demise, as he trusts Justice Wargrave with his life, thus resulting in the ending of his life when he pushed the doctor off the edge of a cliff into the ocean below. Since his corpse went missing, it led to Blore, Lombard, and Claythorne to believe he was the killer. After Blore was killed, Vera saw Armstrong's body which led to Lombard being shot.