The Doctor, Sarah and Harry return to Nerva, but at an earlier point in time. The crew are dying and blame a space plague, but the Doctor suspects a survivor may be responsible.

Doctor Who is Demi's first television role. She has also appeared as Hilde in the stage production of Emil and the Detectives at the National Theatre.

Mark Greenstreet is a British actor who first came to prominence in the 1985 BBC television serial Brat Farrar. First and foremost a stage actor, Greenstreet played many of the great leading roles from the works ofShakespeare, Chekhov and Ibsen to Orton, Wilde and Coward in the UK and around the world in the 1980s and 1990s.

His most high profile screen role is probably the part of Mike Hardy in the BBC horseracing drama Trainer, which was shown from 1991 to 1992. In 1986 he unsuccessfully auditioned for the part of James Bond in The Living Daylights. He played  Ikona in the 1987 Doctor Who serial Time and the Rani.

He directed and co-wrote his first feature film Caught In The Act in 1995 and wrote and directed the highly acclaimed short film The 13th Protocol in 2005.

_{Biography from the Wikipedia article, licensed under CC-BY-SA}

John Abbott played Vince Hawkins in the 1977 Doctor Who story Horror of Fang Rock.

 Director Paddy Russell cast him in the role after seeing him play Snoopy in a play in the Edinburgh Fringe. 

Also worked on Trial & Retribution, Touching Evil, Wycliffe, The Commissioner, Casualty, Expert Witness, The Governor, The Young Poisoner's Handbook, Bottom, EastEnders, The Bill, May to December, Four Weddings and a Funeral, The Chief, Revenge of Billy the Kid, Soldier Soldier, Agatha Christie: Poirot, Kappatoo, Spatz, Treasure Island, Magic Moments, A Hazard of Hearts, The Bretts, Slinger's Day, Lady Jane, Bergerac, Sunday Night Thriller, Angels, Measure for Measure, Edward & Mrs. Simpson, Grange Hill, Moody and Pegg, Special Branch, Paul Temple, Softly Softly: Task Force, Z Cars, Timeslip

Bernard Martin played a control room assistant in the 1970 Doctor Who story The Ambassadors of Death.

Also worked on The Bill, A Dorothy L. Sayers Mystery, Auf Wiedersehen, Pet, Warship, A Little Bit of Wisdom, Dixon of Dock Green, The Regiment, The Big M, Bat Out of Hell, Richard the Lionheart

Marcus Dods was the Incidental music Conductor for the 1964 story Doctor Who serial The Aztecs.

Was the conductor on over 90 television series and Films including the Life of Brian.

Alan Wheatley was a radio announcer who turned to stage and screen acting in the 1930's. He featured in many British films and television productions during the black and white era.

Wheatley left his job as an industrial psychologist to start an acting career. He made his film debut in the 1936 movie Conquest of the Air. During the Second World War, he worked for BBC Radio, both as an actor and as an announcer.

He is probably best known for his role as the Sheriff of Nottingham in the TV series The Adventures of Robin Hood in the 1950s, where he played the malevolent adversary to Richard Greene's Robin Hood. 

He had roles in Danger Man and The Avengers; and was the first person killed by a Dalek in an episode of Doctor Who, when he played Thal leader Temmosus in 1964. He was also an early Sherlock Holmes in a 1951 BBC TV series.

His film credits include: Caesar and Cleopatra (1945), The Rake's Progress (1945), Brighton Rock (1947), Calling Paul Temple (1948), Spaceways (1953), Simon and Laura (1955), A Jolly Bad Fellow (1964), and Tomorrow at Ten (1964) amongst others. He also appeared in Inn for Trouble (1960), a big screen spin-off from the popular TV comedy series The Larkins.

On stage he played Clifford Bax's The House of Borgia in 1935, as well as taking the lead in This Way to the Tomb - performed in London and Paris. He also played the tormented soul, Harry, in The Family Reunion.

Alan Wheatley also collaborated with the BBC English by Radio in a series of programmes for teaching English. He acted as "grandfather" in the series Ann and her Grandfather together with Brenda Cleather who acted as his granddaughter. 

Heplayed the Abbe in the BBC radio series The Count of Monte Cristo with the young Andrew Sachs playing Dante.

He died in Westminster in 1991 of a heart attack, at the age of 84.

Born in Liverpool in February 1946, Elisabeth Sladen took an interest in acting from an early age; she joined the Liverpool Playhouse repertory company as assistant stage manager after drama school, where she would meet her future husband Brian Miller. After a stint touring the country in repertory, she settled in Manchester, during which she had her breakthrough television role in 1970, appearing as Anita Reynolds in Coronation Street. More small roles were to follow in popular shows like Doomwatch, Z Cars and Some Mothers Do 'Ave 'Em.

Then in 1973 came what would be her defining role as she was cast as the replacement companion for third Doctor Jon Pertwee. Following in the footsteps of popular companion Jo Grant played by Katy Manning, Sladen was to hit the ground running as investigative journalist Sarah Jane Smith in her debut story The Time Warrior, and over the next three years would see her popularity soar as she became part of what is arguably known as the "golden years" of Doctor Who alongside fourth Doctor Tom Baker, an era including the story frequently appearing top of fan polls, Genesis of the Daleks.Despite choosing to leave the programme in 1976, with an emotional departure scene at the conclusion of the serial The Hand of Fear, 

Sladen later stated in interviews that although she had left Sarah Jane, "Sarah Jane never left me". Although she declined producer John Nathan-Turner's offer to come back as support for the Fourth Doctor's regeneration (being present at his own arrival at the end of this week's DVD release Planet of the Spiders), she did returned to the role for the 1981 pilot: having been described by the Doctor as his best friend, Sarah was form her second long-lasting partnership with his "second-best friend" in the titular K9 and Company.Sladen was re-united with "her" Doctor, Jon Pertwee, in the 1983 20th anniversary celebration The Five Doctors, and again during the 1990s for the two radio stories The Paradise of Death and The Ghosts of N-Space, written and produced by the person who originally cast her, Barry Letts - the two would also be joined by another popular Doctor Who legend in the form of Nicholas Courtney as the Brigadier.

Philip Locke was an English actor who appeared in the 1982 story Four to Doomsday.

He is possibly best known for his role as villainous SPECTRE underling Vargas in the 1965 James Bond film Thunderball.

He trained at RADA and played many Shakespearian characters at The Royal Court Theatre.

On television, he appeared in : The Baron, The Avengers, The Saint, The Champions, Department S, Z-Cars, Pennies from Heaven, The Omega Factor, Bergerac, Inspector Morse, Jeeves and Wooster, Minder, Antony and Cleopatra, and Ivanhoe.

A member of the Royal Shakespeare Company, he also played "Professor Moriarty" on Broadway in Sherlock Holmes in 1974-76 and appeared in Amadeus at the National Theatre.

Tony Beckley  was an English character actor. A graduate of the Royal Academy of Dramatic Art, Beckley went onto carve out a career on film and television throughout the 1960s and 1970s often playing villainous roles, as well as being a veteran of numerous stage productions.

He was best known for playing the villainous Harrison Chase in the 1975 story The Seeds of Doom. 

He made his film debut in 1965 as Ned Poins in Orson Welles' Chimes at Midnight, and appeared in a number of films for director Peter Collinson: The Penthouse (1967); The Long Day's Dying(1968); and most memorably as Camp Freddie in The Italian Job (1969).

His only starring role was as the psychotic Kenny Wemys in The Fiend (1972), and he made his last film appearance in 1979 playing another psychopath in When a Stranger Calls. Other films include The Lost Continent (1968), Get Carter (1971), Assault (1971), Sitting Target (1972), Gold(1974), and Revenge of the Pink Panther (1978).

Television credits include The Saint, Z-Cars, Manhunt, Callan, Jason King, Special Branch, and perhaps most notably as the villainous Harrison Chase in the Doctor Who serial The Seeds of Doom.

Beckley was terminally ill at the time of filming When a Stranger Calls in 1979, and died of cancer shortly after principal photography was completed (spring 1980).

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