This is a brilliant film if your a massive Sci-Fi fanatic!. It was also known as Doppelgänger as that was the name of the shuttle in the film! . A two man mission to a planet on the opposite side of the sun apparently ends prematurely when the astronauts return to Earth three weeks ahead of schedule, which is just a brilliant storyline!! Pure genius!!. It is a typical 60's production in the way of the style! With sets, costumes and cars that were to be used in Gerry Anderson's next project UFO. He even used a few actors that would also star in UFO such as Ed Bishop, George Sewell, Vladek Sheybal, Keith Alexander, Norma Ronald, Jon Kelley, Philip Madoc, Jeremy Wilkin, Anthony Chinn and Annette Kerr. However the story is a complete mindbender and will be eager to find out the outcome! I didn't get it at first when I watched it for the first time but the more you watch this film, the more you understand what it's all about!! Highly recommended for any Sci-Fi fans out there!!! Enjoy!!!