Captain Brown, in Gerry Anderson's Captain Scarlet And The Mysterons, was the original field partner and close friend of Captain Scarlet, along with whose original incarnation his own was also killed, and likewise replaced with a Mysteron likeness, in the episode "The Mysterons."
The following history assumes that Captain Brown's real name was Alan Stephens.
Stephens left college and joined the World Army Air Force, where he gained degrees in aerospace design management, metal structural engineering and space related mathematics. His superiors were greatly impressed by his capacities in these various fields, and so they promoted him to head the organization responsible for research and development on a new top secret space ship project called ’Zero X.’
His success with the Zero X project led to Stephens working on a new, even more secret assignment: the design of the floating headquarters of a new security organization, to be called Spectrum. While working on this project, Stephens became a firm friend of Colonel White’s. White recognized Stephens’ expertise with cameras and electronic surveillance, gained during his time in the WAAF. Considering these skills, and his involvement in the conception of Cloudbase, Stephens was one of the first men to be chosen to become a Spectrum captain, and he received the codename of Brown.
In the year 2068, after their complex was attacked, illegally and without legitimate provocation, by Captain Black, the Mysterons vowed "slow but nonetheless effective" retaliation and declared a war of nerves, which would ultimately lead to the end of all lives on Earth. The first act of retaliation they threatened Earth with was the assassination of James T. Younger, President of the World Government of Earth. Colonel White gave Captain Brown his first taste of a field command by assigning him and Captain Scarlet to protect the World President.
While Captain Brown and Captain Scarlet were driving to the rendezvous, presumably through the Adirondack Mountains in New York State, the Mysterons made their move, and both were killed as normal Earthmen when their Spectrum saloon car was forced to crash and career down a ravine. Both men were Mysteronised; Captain Brown’s death was so instantaneous (from a broken neck) that he never knew what had struck him. Captain Scarlet, his field partner, was not so fortunate.
Captain Brown, Mysteron AgentEdit
The Mysteron sent their likeness of Captain Brown to assassinate the World President at Spectrum Maximum Security building.
When they arrived at the building and headed to the President's new suite, the Captain Brown likeness tried to kill the World President by turning into a smoking bomb. However, the President noticed the smoke pouring from the Spectrum agent's tunic and pressed an emergency button on the arm of his desk chair, whisking him away to safety while the building blew up. The first Mysteron attempt on his life had failed.
At Cloudbase, he and Colonel White watched a video tape of the incident, leading both of them to believe that Captain Brown had had a bomb concealed in his tunic, and that it was a trigger for a larger device planted in the building.
They were amazed by what had happened, for the Colonel said that Captain Brown had been "one of [his] finest men." It was not until later that he learnt that the corpse of the original Captain Brown had been found and the other was a Mysteron.
The following information, provided by http://www.Spectrum-Headquarters.com/, assumes that Captain Brown's real name was Steven Blackburn, as established by Mary J. Rudy in her contributions to http://www.Spectrum-Headquarters.com/ and thus accepted in fanon.
Consequently, Captain Brown never received his chance to command any missions till after the events on Mars, and the Mysterons’s first attack. Charged with protecting the World President, he was instead killed and taken over by the Mysterons. Soon after this, his wife, Rebecca Evershaw, left Spectrum and gave birth to a boy, whom she named Steven.