The Passenger (webcast)

 was a promotional mini-episode included on the release of Doctor Who: The Collection — Season 20 Blu-ray boxset.

Synopsis
Tegan Jovanka's adventures continue... but not in the way she expected!

Plot
Tegan receives a message from someone saying "Blue box." Tegan replies asking where and who, but receives only "Tonight. The fairground."

That night at the fairground she reunites with an older Nyssa, confused as to how she came to Earth from Terminus, but Nyssa explains she hitched a ride and indicates the TARDIS. Nyssa offers her the chance to travel again and Tegan enters the TARDIS...

Inside is a dark void and Tegan is met by a pale version of herself. This Tegan offers her the change to fulfill all her desires as she hears Nyssa's voice calling for her. Tegan refuses and her double morphs into the Mara and threatens to consume her-

Tegan wakes with a start in her bed. After looking around the room and seeing everything is fine, she stands before her mirror and defiantly tells the Mara it's seen everything she faced and it's nothing: "Back in your box." She leaves and the skull of a snake appears in the mirror before it cracks and shatters...

Cast

 * Tegan Jovanka - Janet Fielding
 * Nyssa - Sarah Sutton

Uncredited Cast

 * The Mara - Janet Fielding
 * Trailer Voice Over - Peter Davison

Crew

 * Writer, Director & Editor - Pete McTighe
 * Location manager - Andrew Stocker
 * Make-up - Sarah Burrows
 * Camera assistant - Sam Creamer
 * Sound Recordist - Jasmine Allodi
 * Studio D.O.P & Camera - Jeremy Bishop
 * Location D.O.P & Camera - Matt Patrick
 * Visual effects - Chris Thompson
 * Title sequence - Sid Sutton, Charlie Lowe
 * Dubbing Mixer - Mark Ayres
 * Thanks to Adventureland Southend-On-Sea, Melyssa Aylott, Lee Binding, Phil Collinson, Jess Mendoza, Alex Moore, Jeff Parker, Jane Spencer Prior, Matthew Sweet, John Tore Eastmon, Ellis Turffrey, Paul Vanezis and Jordan Webb
 * Executive Producers - Russell Minton and Pete McTighe

Continuity

 * Tegan remembers leaving Nyssa on Terminus, (TV: Terminus) although another account shows Nyssa eventually leaving in E-Space. (AUDIO: The Entropy Plague)
 * Tegan previously met an older Nyssa. (AUDIO: Cobwebs)
 * Tegan has met the Thirteenth Doctor. (TV: The Power of the Doctor)
 * The Mara resurfaces in Tegan's mind for the fourth time. (TV: Kinda, Snakedance, AUDIO: The Cradle of the Snake)
 * The Mara is still with Tegan, which as she feared, is like a terminal disease that could resurface at any time. (PROSE: Goth Opera) The Fifth Doctor had previously speculated that the Mara would leave some part of itself in those it had possessed. (AUDIO: The Cradle of the Snake)