Story & Art: Mac Raboy
Original run: 1953-09-20 to 1954-01-17
Summary: Receiving a visit from Flash at his Earth laboratory, Dr. Zarkov proudly shows off his latest project: a single-seater space ship designed for a reconnaissance flight of Jupiter's fourth moon Callisto.
Happily accepting the chance to man the first solo flight into outer space ever, Flash soon lands near a sprawling city on Callisto, but is severely warned by a lone eremite to beware of “the city of doomed souls”...
(Source of summary: www.ipcomics.net)
All credits go to "spax".