Lost in the universe of antimatter, the Doctor communes with the creature and makes a bargain. Sarah discovers Professor Sorensen's dark secret which threatens to overwhelm him.

The Time Lord takes Clara aboard the world's most luxurious train, where a mummy is terrorising the passengers. Frank Skinner guest stars.

Joseph Tremain (born  in Romford, Havering) is an English actor. 

He has appeared on radio and in theatre, TV and films. He has also appeared in a number of commercials for a variety of products. Tremain made his West End stage début in a production of The Full Monty at the age of 10. He is best known for starring in the first series (13 episodes) of the children's television series Morris 2274 in 2003 for Five television. 

He has also appeared in an episode of Half Moon Investigations for the BBC. He attends the Sylvia Young Theatre School in London.

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

Originally trained in fine art at Goldsmiths college where he began using film as a medium. He started his film career in music videos and commercials.

His first feature ROLLIN¹ WITH THE NINES won best British film at Raindance 2005 and was nominated for best first feature at BAFTA 2006. Ali won best cinematography at the Toronto film festival 2011 for his work on the feature A LONELY PLACE TO DIE, (the feature also won best action film at TIFF). Other films: Doghouse, The Hooligan Factory for Altitude Films, THE WEE MAN (Winner best film at the Scottish BAFTAs, 2013). Soon to be released STILL WATERS.

Currently working on a personal project, Quicksand For Beginners, an installation about the Israeli / Palestinian conflict. 

Nicola Bryant is an English actress known for her role as Perpugilliam "Peri" Brown, a companion of the Sixth Doctor Colin Baker.

Bryant grew up in a village in Surrey, near Guildford. She started dance classes at the age of three and also began to learn the piano. At the age of ten she auditioned to go to ballet schools, but was unable to take up places offered because of asthma. Upset by this development, she joined a local amateur dramatic group. On leaving school, she auditioned for all of the London drama schools and took up a scholarship to the Webber Douglas Academy of Dramatic Art. In her final year there, she played the part of Nanette in a production of the musical No, No, Nanette.

Bryant's first professional part was as Peri Brown in Doctor Who. She played the part from 1984 to 1986, first with Peter Davison, and then with Colin Baker as the Doctor.  Her character was American and for a while a publicity-driven fiction was maintained suggesting Bryant was also American. 

After appearing in Doctor Who, Bryant spent nine months at the Savoy Theatre in the West End of London in the thriller Killing Jessica with Patrick Macnee, directed by Bryan Forbes. She went on to have other television roles, including a part in Blackadder's Christmas Carol. In the early-mid 1990s, she also co-starred with Baker in a series of made-for-video science fiction films entitled The Stranger for BBV. She also appeared alongside Baker, Davison, Sylvester McCoy and Jon Pertwee in another BBV production, The Airzone Solution, which is notable as it includes a love scene between Baker and Bryant.

Bryant reprised the role of Peri in several of the Big Finish Productions Doctor Who spin-off audio plays. She has appeared with both Peter Davison and Colin Baker in these. She also directed UNIT: The Wasting and Judge Dredd: 99 Code Red!.

In February 2006, she performed in a New End Theatre production of the Carl Djerassi play Taboos, and in early 2007 appeared in a London stage production of Tom Stoppard's Rock 'n' Roll at the Duke of York's Theatre. A DVD documentary, In The Footsteps of The Two Doctors, following Nicola's return to some of the locations featured in the Doctor Who serial The Two Doctors, was released in late 2006.

She returned to the stage in 2008/2009, in a touring production, in an adaptation of Daphne du Maurier�s Don't Look Now, playing the part of Laura Baxter.

In the summer of 2009 Bryant filmed an improvised documentary-style film for award-winning Australian director Ben Briand for the European arm of a travel company, as well as recording eight stories for a missing season of audio adventures for Big Finish's range of Doctor Who CDs.

Roy Herrick was a British actor.

His television credits include: Danger Man, Public Eye, Callan, The Regiment, Colditz, Survivors,Pardon My Genie, George and Mildred, Tenko, The Fourth Arm, Mr. Palfrey of Westminster and Howards' Way.

He appeared in two Doctor Who stories: as Jean in The Reign of Terror and Parsons in The Invisible Enemy. He also voiced Xoanon in the Doctor Who story The Face of Evil.

Roy also played the barman in two episodes of You're Only Young Twice - 'The Missing Ring' and 'The Home Perm'.

John Angus Basil Crockett was a stage and television director. He was the second son of Colonel Basil Crockett DSO.

He directed the Doctor Who story The Aztecs in 1964, one of the most highly regarded of the black and white stories. In the 2002 DVD release of the story, the actor John Ringham is effusive in his praise for Crockett.

In 1939, he was a student of Art at Goldsmiths' College, New Cross, London, UK.

In 1944 he established a theatre company called The Compass Players. It was a travelling company that intended to perform high quality theatre to audiences who would not normally have access to it. During this time Crockett met his wife to be, Anne Marguritte Stern, first daughter of Dr. William Joseph Stern OBE, an eminent physicist. They raised their family in the Cotswolds, where he continued to paint.

In the late 1950s and early 1960s, John produced a number of plays for both the Birmingham Repertory Theatre and the Dundee Repertory Theatre.

From Sept.1969 until Dec.1976 he was a teacher of Art and Drama at Downside School (Somerset, UK.), where he sent one of his three sons, Dr Antony Crockett FRCGP.

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