Complex sentence: Ritter is assisted by a Nazi government official, SS/Gestapo Hauptsturmführer Martin Vogel (Roy Thinnes)--he poses as official photographer--- although both operate independently in investigating the background of all passengers and crew on the voyage.
Split into simpler sentences: Ritter is assisted by a Nazi government official, SS/Gestapo Hauptsturmführer Martin Vogel (Roy Thinnes), who poses as official photographer. However, both operate independently in investigating the background of all passengers and crew on the voyage.