"Wargrave says he wrote the manuscript because he takes an artist’s pleasure in his own work and wants recognition. He wonders if the police will pick up on three clues: first, that Wargrave was the odd man out—he was not really guilty of a murder, as the rest were, since in condemning Edward Seton to death he condemned a guilty man. Second, the line about the “red herring” points to the fact that Armstrong was somehow tricked into his death. Third, Wargrave’s death by a bullet through the forehead will leave a red mark like the brand of Cain, the first murderer in the biblical book of Genesis."
http://www.sparknotes.com/lit/andthenthere/section10.rhtml
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