Before the Hop Harrigan story continues we look across stories of great pioneers men and women who had courage enough to face the unknown, courage enough to go up in a ship when they didn't know whether they'd come down in one piece. One of these is Glen L Martin, owner and founder of The Martin Company and builder of many great planes. 

And now to our story. With the murder of an air mechanic the riddle of the ghostly avengers has taken a deadly turn and Hop and Tank are in serious trouble.