Doctor Who: The Newbies Guide
This is the first story in Season 26.
The seventh Doctor is fond of mixed metaphors and malapropisms and carries an umbrella with a question mark handle. He is more prone to plan and take proactive action against his foes than his other incarnations.
Ace (real name: Dorothy McShane) is a teenager from 1980s Perivale, London. She is interested in explosives, and has invented one called Nitro Nine. Whilst experimenting with it, she was caught up in a timestorm and ended up on the planet of Iceworld. In Dragonfire she met the Doctor and joined him on his travels. She has the habit of calling the Doctor "Professor" and sometimes using nicknames for other people she encounters.
Recurring and Historical Characters
Alistair Gordon Lethbridge-Stewart was the commanding officer of the United Nations Intelligence Taskforce (UNIT). He first encountered the Doctor in his second incarnation (The Web of Fear and The Invasion.) In Spearhead from Space, he teamed up with the Third Doctor to prevent an invasion by the Nestene and the Autons. During that story he persuaded the Doctor to work as his scientific adviser. Since then he has worked with multiple incarnations of the Doctor to protect Earth from alien threats. Even after he retired from UNIT.
The United Nations Intelligence Taskforce is an international military force set up to protect the Earth from alien threats. Its British branch used to be commanded by Brigadier Lethbridge-Stewart and the Doctor's third and fourth incarnations worked as UNIT's scientific advisor.
The novelisation provides a brief glimpse into the future adventures that this story is a sequel to.