The alien intelligence, the Animus, coerces the Doctor into tracking down the Menoptra. Ian escapes the Carsinome and joins forces with Vrestin, but the Zarbi are in pursuit.

The Master forms an uneasy alliance with the Doctor so that between them they can subdue the Keller Machine which is now out of control.

Nikki Amuka-Bird is an English television, stage and film actress. Her theatrical credits include Welcome to Thebes (National Theatre); Twelfth Night (Bristol Old Vic); World Music (Crucible Theatre, Sheffield and Donmar Warehouse); Top Girls (Oxford Stage Company); A Midsummer Night's Dream, The Tempest and The Servant of Two Masters(Royal Shakespeare Company); Doubt: A Parable (Tricycle Theatre).

Her film credits include The Omen (2006 remake), Cargo, Almost Heaven as well as the screen adaptation of Alexander McCall Smith's novel The No. 1 Ladies' Detective Agency. On television, she has appeared in Spooks, The Line of Beauty, The Last Enemy, Robin Hood, Torchwood, and a recurring role in the reimagined BBC apocalyptic series Survivors. In 2010 she appeared as Det Supt Gaynor Jenkins in the BBC's Silent Witness.

She appeared in the BBC adaptation of Andrea Levy's award winning novel, Small Island, broadcast in December 2009.

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

Tom Chadbon (born in Luton, Bedfordshire, England, UK) is an English actor, who has spent the larger part of his career appearing on British television. While principally acharacter actor, he has occasionally had leading or recurring roles.

Among his more regular work, he helmed all 10 episodes of 1995's Crown Prosecutor, playing the almost-titular Lenny Monk. He also enjoyed substantial recurring roles on Chancer, Where the Heart Is, and Wire in the Blood.

The majority of his career, though has been spent building a long résumé of featured guest work on a large number of British television shows, including: Out of the Unknown, The Stone Tape,Softly, Softly, The Liver Birds, Blake's 7, Tales of the Unexpected, The New Statesman, Between the Lines, Peak Practice, Casualty, Hetty Wainthropp Investigates, Silent Witness, The Bill, Holby City, Heartbeat, Foyle's War,Midsomer Murders, Rebecca, and Taggart.

The guest role seen by the most number of people, however, was that of Duggan in the Doctor Who serial City of Death, He would later return to Doctor Who as Merdeen in the 1986 story, The Trial of a Time Lord. He has also been an occasional guest star in Big Finish audio productions. Most notably, he played the recurring character of Will in the second series of Sarah Jane Smith audio adventures. He also had a featured guest role in No More Lies, during Paul McGann's 2007 broadcast season on BBC Radio 7.

Though his theatrical film work has been more sparse, he had a small role in the 2006 James Bond film, Casino Royale.

He plays a semi-regular character, Professor Henry Williams, in the 23rd series of Casualty, which is currently being aired on Saturday nights.

Derek Ware is an English actor and stuntman, active from the late 1950s through the 1990s. 

He is best known as a stuntman and fight arranger for the early seasons of Doctor Who, although he also worked on EastEnders, Z-Cars, and other British productions.

Richard McNeff played Baker in the Doctor Who television story The Dalek Invasion of Earth.

Also appeared in The Wilsons, Chance in a Million, Cowboys, Born and Bred, Armchair Thriller, Hazell, London Belongs to Me, Three Piece Suite, Warship, The Rough with the Smooth, Some Mothers Do 'Ave 'Em, Justice, And Mother Makes Three, Softly Softly: Task Force, The Rivals of Sherlock Holmes, Comedy Playhouse, The Laughing Stock of Television, Special Branch, Callan, Dixon of Dock Green, Up Pompeii!, The Mind of Mr. J.G. Reeder, Z Cars, ITV Playhouse, The Baron, The Marked One, Redcap, The Big Spender, No Hiding Place, The Saint, The Brain, Emergency-Ward 10, The Painted Smile, Emergency, Our House, Dangerous Afternoon, The Odd Man, Jungle Street, Precious Bane, Suspended Alibi, ITV Play of the Week