Marianne Kyle was an inhabitant of the Inferno Earth.
In the 1950s she was an officer in the British Army stationed at a military base near Leipzig in Germany. In 1959 she conducted a lengthy experiment interrogating Lethbridge-Stewart, believing him to be an agent of a foreign government. Along with James Lethbridge-Stewart she was one of the founder members of the Republican Security Forces. (PROSE: The Schizoid Earth)
She was one of the survivors after Eric Stahlman's project nearly destroyed her world. After capturing Koschei, they used him to try to escape to this Earth. Kyle became the Master's accountant for a time. The Master eventually destroyed the dimensional link between the two worlds, stranding Kyle from her Earth. (PROSE: The Face of the Enemy)