Despite the title, The Underworld featured better than average action crime stories, mainly by authors unknown today, most initially reprinted from other Munsey titles. Launched in 1927 it ran for 93 issues under a variety of title variations before folding in 1935.
A British reprint edition ran for a while in the 1930s.
SYSTEM—JAMES B. HENDRYX
THE SQUEALER—WILLIAM ALLEN WARD
THE DEADLY CIRCLE—CHARLES J. SULLIVAN
TAKE 'IM ALIVE—WALTER C. SCOTT
THREE DEAD MERCHANTS—FRANK GRUBER
THE RUSE IN COCAINE ALLEY—WILLIAM MAHONEY