Muriel Frost

Captain (later Colonel) Muriel Frost worked for UNIT. On a number of occasions, she worked with the Doctor's seventh incarnation.

Profile
A fiery redhead, both in hair colour and temperament, Frost was a no-nonsense and efficient UNIT operative who nonetheless had problems maintaining personal relationships.

Her first direct encounter with the Doctor happened when, Working undercover, Frost and investigated Stranks, the owner of a night club suspected of selling a potent street drug called Mandrake. At the same time, the the Doctor and Ace had been drawn to Earth at the close of the 20th century by the alien energy structure known as the Mandragora Helix, which in an earlier incarnation, the Doctor had last encountered 500 years before. When told of Frost's investigation, the Doctor pointed out that another name for Mandrake was Mandragora. The similarity in names was no coincidence. The Mandragora Helix had contacted Stranks and used him to produce Mandrake, which sapped the will of its users, making them susceptible to the Helix's influence. Together with Frost, the Doctor and Ace thwarted the Helix once again. During the course of this venture, she received a field promotion to Colonel. (DWM: The Mark of Mandragora)

Now a Colonel (the result of a field promotion towards the end of the previo), and investigating the crash of a World War II fighter plane. With the help of the Doctor Frost entered the mind of the dead pilot and discovered that the crash was a result of a collision with an alien spacecraft. The local records clerk, Alex Evening, had taken possession of the miniature alien craft and was using its abilities to turn fantasy into reality to kidnap beautiful women, placing them in an imaginary empire of his own creation. The Doctor and Frost entered Evening's empire with UNIT troops and managed to destroy the illusion, sending Evening into an irrecoverable coma. (DWM: Evening's Empire)

Other timelines
In a world where Humans had a working relationship with the Silurians, Frost was a member of URIC, that world's equivalent to UNIT. (DWM: Final Genesis)