Using his infected Claw, The Black Hand can touch a person and infect them with a disease that quickly causes their skin to blacken and their death. The Black Hand kidnaps and tortures John Townsend for the plans to an Army targetting device. When John won't talk, the villain brings John's son Tom before slaying John for refusing to talk. The Black Hand decides to kill Tom Townsend as well, but Yank, a large eagle, rescues Tom and carries the rakish youth to his aerie. With Yank's hospitality and care, Tom recovers. One day, Yank brings Tom an American flag. Tom swears to fight for the United States, donning the costume and moniker of Captain Flag. He summarily defeats The Black Hand and his mob.