Deep Blue (novel)

 was the twentieth BBC Past Doctor Adventures novel. It featured the Fifth Doctor, Tegan Jovanka and Vislor Turlough. It also featured UNIT, Brigadier Alistair Gordon Lethbridge-Stewart, Captain Mike Yates and Sergeant John Benton. Also, it sees a character development for Tegan, with her falling in love in this novel.

Publisher's summary
''When a lighthouse keeper reports seeing a ball of light plunging into the sea off Tayborough Sands, UNIT sends Mike Yates to investigate. The last thing he expects to find there is an old friend — with a new face...'' The Doctor and his companions arrive on a pleasure beach in the 1970s, hoping for time off after their latest adventures. But they do not get to relax for long. Violent incidents are at an all time high in the area and people are going missing - or else changing into something more than human...

The Doctor soon realises a sinister presence lurks in the cold seas off Tayborough Sands - a presence with sinister designs on humanity.

Plot
to be added

Characters

 * The Doctor
 * Tegan Jovanka
 * Turlough
 * Brigader Lethbridge-Stewart
 * Mike Yates
 * Sergeant Benton
 * Derek Etkins
 * PC Andy Weathers
 * Tony Maybury
 * Imogen Maybury
 * Charlotte Maybury
 * Chris Maybury

The Doctor

 * The Doctor refers to his third incarnation as "arrogant" and "overbearing".
 * The Doctor carries his UNIT pass with his third incarnation's photograph on it.
 * He buys a 99 ice cream with glittering purple shells.

Spacecraft

 * The ship that invades is a modified Morok battlecruiser.

Technology

 * The Doctor uses the IRIS machine.

Species

 * The Xaranti are intergalactic scavengers with a hive-like mind structure and a breeding programme that involves telepathically infecting other races to develop into Xaranti. They look "part bull, part spider, part scorpion". Their homeworld was destroyed in the war with the Zygons.

Continuity

 * From UNIT's point of view, this story takes place after TV: The Green Death.
 * Mike Yates is still recovering from the events of The Green Death.
 * The Doctor mentions the Zygons. (TV: Terror of the Zygons)
 * The Doctor, Tegan and Turlough are spending a vacation in order to recover from the events of TV: Warriors of the Deep.
 * Tegan last saw her grandfather just before he was about to move house and had promised to visit him as soon as she returned from Amsterdam (TV: Arc of Infinity) and thinks of visiting him. She would do so later on TV: The Awakening.
 * The Doctor tells Mike Yates that he has regenerated twice since he last saw him. (TV: Planet of the Spiders, Logopolis)
 * Turlough is worried that he meets the Brigadier now, but the Brigadier didn't recognize him later when turns up as a pupil at the school where he teaches Maths. (TV: Mawdryn Undead)
 * Tegan remembers being possessed by the Mara. (TV: Kinda)