Hell Hammers Harbin

Published in Flying Aces, March 1938.
"QUESTION MARK OF DEATH! North! North! And still farther northward over those bleak wastes of Asia flew Dick Knight. His course was uncharted—his destination unknown even to himself! Only a question mark—a cryptic crimson
question mark emblazoned on a rough Manchurian map—offered a clue to the mystery of that mad flight. And that puny clue was destined to be his single weapon against—hideous meteors of murder!"