Purple Death from Outer Space (DVD)

Earth men are stricken with a mysterious disease that causes instant death and leaves a purple mark. Dr Zarkov discovers a spaceship from the planet Mongo and realizes this is the source of the plague. Flash Gordon, Dr Zarkov, and Dale Arden learn of an antidote but getting it will be no easy task, going up against an army of humanoid robots controlled by Ming the Merciless.