| Professor Robinson inadvertently opens a door to another dimension where his evil double resides and plots to invade the Robinsons' planet. When Robinson is kidnapped, Smith, Will and the robot must venture into the Anti-Matter world to rescue him.
As the show begins Will is reading to Smith from a huge antique volume-a chapter entitled "The Shadow World". It's an effective opening but how are the anti-matter men able to turn the pages of the book from another dimension? And how, later in the episode is Will's real dad able to communicate with Will from there as well? Are these hints of psychic powers never again explored in this episode? The first face-to-face encounter between John and his counterpart is well directed also, as are the following scenes where the camera zooms in so close to the robot, in a state of panic, until he is all one can see on the screen. Once again, Bob May in the robot costumes turns the upper half of the suit around 360 degrees-surely no easy feat.
The anti-matter Don (cleverly named Drun) remarks in a whisper that he and John's evil twin have been waiting "thousands and thousands and thousands of years" to escape their world. Why have they existed for so long? Is that the writer's idea of the opposite of the finite lifespans of the Robinsons and West?
There are obvious 'bloopers,' for lack of a better word, in this episode. As the robot gets up from the rock on which he's been sitting to help Will re-activate the Atomizing Unit Bob May's legs are clearly visible, as is Bob's right foot a few seconds later. Later in the episode when Will and the robot are menaced in the anti-matter world by the moving rocks (Priplanus leftovers hastily painted white) the shadow of the technician pushing the rock is clearly visible in full profile. And the anti-matter Robinson is not supposed to cast a shadow ("Even in strong sunlight," remarks the robot to Will) but in every scene he does. These are three very sloppy errors on the part of the production crew and everyone involved.
Will and the robot rescue someone they believe to be John Robinson from the alternate universe but of course in reality it's the bad guy instead. As Will and the robot discuss how to rectify this situation once they learn the truth, Guy Williams at his acting best as his evil opposite is hiding in the Space Pod bay, eavesdropping. He grabs a lead pipe from the storage locker and, angrily smacking it against his palm, chases the boy and the robot. The stunt double robot suit is used as Robinson beats the robot into unconsciousness with the pipe and knocks the mechanical man to the ground. This is clearly not a homogenized Lost in Space show from season two but instead a violent, dark chapter in the history of the Robinson family. This could account for its popularity among both the cast, the director and the fans.
Will searches the anti-matter world for his real father and discovers the cave where John is held prisoner, guarded by Drun and an alien creature whose presence is never explained. The robot stunt costume is used again now painted black and white like the costumes of the anti-matter people and sports a green "mouthpiece" instead of the standard red one. He is mean and untrustworthy and presumably imprisoned horizontally in his cage for all time.
Eventually the real John escapes his cage in a thrilling duel with the witless and violent-tempered Drun featuring a flaming torch and and some fancy footwork courtesy of Guy's stunt double Joseph Canutt, son of the legendary stuntman Yakima Canutt. Joseph had been Stephen Boyd's double in the Ben Hur chariot scenes and the stunt co-ordinator for films like Planet of the apes, Earthquake and the Omega Man. Canutt is used again in the climactic fight of John vs. John on the inter-dimensional walkway. It's obvious neither is actor Guy Williams but it moves so fast and is choreographed so well that's it's exciting to watch nonetheless.
According to director Sutton Roley during the filming of the walkway scenes everything looked ridiculously phoney. A large black screen was set up and colored fragments were tossed onto its sticky surface but the results every time were disappointing. No matter how hard they tried it looked, in Sutton's words, "hokey." When Roley saw the finished product, thanks to the magic of editing, lighting, and trick photography, he was impressed and later commented he considered it one of the best episodes he directed for Irwin Allen.
Guy Williams was seriously considering exiting Lost in Space after season two, unhappy with scripts that invariably featured his television son, Dr. Smith and the robot. He wanted to produce a televison spoof of Sherlock Holmes but was talked out of it by Irwin who promised better scripts featuring the John Robinson character such as this one in season three. The three hundred fifty dollar a week raise (pretty good by 1967 standards) didn't hurt either. According to the late Guy's family "The Anti-Matter Man" was his favorite episode from the last two seasons and it shows how much he enjoyed it in his acting. The anti-matter Robinson is nothing like "our" John-his facial expressions, posture, even his voice is totally alien. The viewer wants to scream at the screen "That's not John! Can't you tell?"
Smith is tossed in almost as an afterthought throughout the episode, appearing only incidentally in most scenes, certainly unnecessary in the show's climax. Perhaps this is another reason this is a fan favorite with die-hard Lost in Space purists , aggravated by Jonathan's overexposure in the previous seasons.
Much of the music by John Williams was recycled from the "Reluctant Stowaway" premiere but was used appropriately in the right places. Despite its shortcomings this IS one of the series' best episodes and not to be missed.
According to the Book "Lost in Space Forever" published by Windsong Press in 1992 the original opening for the show was scrapped in favor of the "Shadow World" beginning. Also, the second anti-matter man was not going to be a member of the Robinson party but was thankfully changed to Drun, a bearded, scarred version of Major West.