Harcourt Brown (George Coulouris) takes Margaret Henderson (Hester Cameron) hostage in the rocket’s control room. He locks the hatch so no one can get in. Conway Henderson (Gerald Flood), Geoffrey Wedgwood (Stewart Guidotti) and Professor Mary Meadows (Pamela Barney) are in the main section of the rocket. To gain their cooperation he threatens to let the oxygen out of their section should they try to gain access to the control room. He informs them that he intends on flying the spaceship to Mars.
Brown has been sending furtive radio messages from time to time fully believing that he is communicating with Martians. He believes that when they get to Mars, the Martians will assist him in landing the ship on the planet’s surface.
Brown informs Henderson that they have fifteen minutes to get anything they need from the supply ship. After that he will disengage from the supply satellite and head for Mars. Believing that Brown is crazy enough to kill them all, they have no choice but to comply and hurry and get the supplies on board.
Meanwhile, the control room on Earth has lost all contact with the MR-4. They can see that the ship has left the docking station of the supply ship and is heading off into space. All they can do is theorize that Brown has taken over the ship and is heading toward Mars.
Henderson comes up with a plan to try to take back the ship. Using Morse Code, Geoff alerts Margaret of the plan. To execute the plan Henderson needs to do a spacewalk and cut the power to the temperature controls of the ship. While Henderson is outside Brown sees what he is trying to do through the ships periscope and tries to shake him from the ship. Geoff manages to pull Henderson back into the ship before he is thrown into space.
By the time the ship has been in space for three weeks the water supply is almost out. Margaret becomes dehydrated and ill. Since they are too far out to turn around Brown allows Henderson to tend to Margaret.
Eventually they reach Mars and prepare to land, but they have no idea what they will find.
George Coulouris’ character Harcourt Brown is proving to be MR4’s version of “Lost in Space’s” Dr. Smith. At times his character is cutthroat and evil and at times he is kind and caring. He thinks nothing of letting everyone die to get what he wants but will take the effort to save a guinea pig from suffocating.
I’ve seen some criticism about the show sending kids into space on a whim. Yes, it is farfetched, but we are talking fantasy here not reality. No one has a problem with a police call box being bigger on the inside and children being whisked by an alien through time.
The Pathfinder series were very popular with both adults and children. This episode aired on Christmas Day 1960. Viewership was second only to the Queen's Speech.