Doppelgänger (released internationally as Journey to the Far Side of the Sun) is a 1969 British science fiction film written by Gerry and Sylvia Anderson and Donald James, produced by the Andersons, and directed by Robert Parrish. Filmed by the Andersons' production company Century 21, it stars Roy Thinnes, Ian Hendry, Lynn Loring, Loni von Friedl and Patrick Wymark. Set in the year 2069, the film concerns a joint European-NASA mission to investigate a newly discovered planet which lies directly opposite Earth on the far side of the Sun. The mission ends in disaster and the death of one of the astronauts, following which his colleague realises that the planet is a mirror image of Earth in every detail, with a parallel and duplicate timeline.

Plot

In 2069, the European Space Exploration Council's (EUROSEC) Sun Probe discovers a planet in the same orbital path as Earth on the far side of the Sun. The findings are transmitted to a power in the East by double agent Dr Hassler. Tracing the messages to Hassler's laboratory, Security Chief Mark Neuman corners the scientist and kills him.