Superman must find out the identity of the mysterious gang leader known as the Unknown X who has organized one of the most thorough criminal organizations Metropolis has ever seen.
Written By:Bill Finger, Henry Boltinoff, Jerry Siegel, Gardner Fox, Ed Moore, Jack Lehti
Pencils:Bob Kane, Stan Aschmeier, Henry Boltinoff, Howard Purcell, John Wentworth, Harry Lampert, Paul Norris, Ed Moore, Don Cameron, Jack Lehti, Joseph Sulman, Eddie Winiarski, Paul Henry Cassidy
Inks:Bob Kane, Stan Aschmeier, Henry Boltinoff, Howard Purcell, Harry Lampert, Ed Moore, Jack Lehti, Joseph Sulman, Leo Nowak
Cover By:Fred Ray