Helmut Rellergerd (born 25 January 1945), known by the pen name Jason Dark, is a prolific author of horror detective fiction in the German language.

[8] Starting in 1973, Jason Dark wrote horror detective stories of the pulp fiction variety, centred on an English Scotland Yard inspector named John Sinclair.

The plots generally entail Inspector Sinclair's fighting against the forces of darkness (vampires, werewolves, sorcerers, zombies, etc.)

Indeed, Godden writes: "‘As regards imagination, Jason Dark towers houses high in superiority above Sherlock Holmes creator, Conon (sic!)

[9] Helmut Rellergerd has claimed that many people have found his novels to be psychologically and emotionally beneficial, particularly during times of illness (saying that they have contributed to the recovery process through John Sinclair's "optimistic attitude" to life).

When asked in 2006 what caused him the greatest fear and horror, he replied that it was George W. Bush's activities, particularly in Iraq: these called forth veritable goosebumps of fright upon his skin, he said.