It's 1998, and the global information superhighway is about to come online. But an alien species has infiltrated the network.
Sarah Jane Smith and an older Harry Sullivan.
An older Sarah also appears in the epilogue.
Pg 88 We don't see it happen, but the TARDIS is off Kingsbury Mews, 1998.
Pg 305 We don't see how it got there (see Continuity Cock-ups), but the TARDIS is in London.
Pg 21 "Must be the helmic regulators." The Ark in Space.
Pg 22 "I'll try the ginger beer." The Android Invasion.
Pg 49 "I said don't look." The Doctor also uses this line in City of Death.
Pg 57 "Came here a couple of times with the Brigadier, back in my "establishment" days." The Pertwee era.
"He leaned back on the chair and crashed his feet down on the table top, making the telephone receiver jump in its cradle." The Doctor does something similar in The Seeds of Doom.
Pg 59 "I wouldn't have thought you were the UNIT type, to be frank" The Doctor is the UNIT type, and don't call him Frank.
Pg 60 "His competitors keep their thoughts largely to themselves. Except Ashley Chapel, but he's big enough in his own right not to be scared." Millennial Rites
Pg 64 "I got a posting at Porton Down after my assignment to UNIT was up. Defence research stuff, veru hush-hush." This is how the Brigadier describes Harry's career in Mawdryn Undead.
Pg 75 "Then he stuck a jeweller's glass in his eye and went back to work." The Stones of Blood.
Pg 80 The sonic screwdriver makes an appearance (Fury From the Deep et al).
Pg 85 "He should not be burdened with the more sensationalist articles Miss Smith had written for Metropolitan about the potential dangers of meditation and the sudden evacuation of London all those years ago." Planet of the Spiders, Invasion of the Dinosaurs.
Pg 88 "Name: John Smith" The Doctor is still using his alias from Spearhead from Space.
"He picked out odd words and phrases, like 'Prydon Academy' and 'Lister, 1880' but little of it seemed to make sense." The Deadly Assassin, The Moonbase.
"'I'm ideally suited to the post of scientific advisor, if you need such a thing.' the Doctor said. 'I have had considerable experience in such areas.'" Spearhead from Space et al.
Pg 99 "She thought they took up whole rooms before they had any real processing power. But that, she had to keep reminding herself, was nearly twenty years ago." Since it's 1998, this suggests that Sarah's time post-dates 1978, typing in with Pyramids of Mars and contradicting the Brigadier's 1977 retirement in Mawdryn Undead. So UNIT Dating is still intact, then.
Pg 105 "When the door swung open a few seconds later, he was standing idly in the far corner of the room playing with his favourite yo-yo." The Ark in Space.
Pg 111 "The Doctor asked him about the feasibility of involving UNIT, but Harry was opposed to that. The Brig had long since retired, and there was a new chap - Bam-something." Battlefield.
Pg 119 "He had been expecting flashing lights and LEDs, although he knew from Nerva that this was a somewhat romantic notion." The Ark in Space/Revenge of the Cybermen.
Pg 140 "I am the scientific advisor to UNIT." Spearhead from Space et al.
Pg 141 "But then he reflected on the size of some of the boot cupboards in the TARDIS and looked in anyway." The Masque of Mandragora.
Pg 146 "Harry missed his old MG." Harry Sullivan's War.
Pg 198 "Higgins could almost imagine him whistling Colonel Bogie." As indeed he does in The Talons of Weng-Chiang.
Pgs 209-210 "He could survive without oxygen for a comparatively long period of time - much longer if he went into a trance." Terror of the Zygons, Pyramids of Mars.
Pg 222 "He had watched a wobbly series of Nightshade from what seemed like centuries ago" Nightshade.
Pg 234 "'Your enforced separation from this world.' The Doctor sighed. 'Not again,' he said. 'I went through something similar a few centuries ago.'" It's unclear if this is referring to his exile to Earth or his originally leaving Gallifrey.
Pg 241 "You know the history, you can probably talk about thetechniques used - the wide brush strokes, the lightly watered colour." Not dissimilar to how the Doctor talks about Da Vinci's work in City of Death.
"But you don't appreciate it" Possibly echoing the Doctor's line in The Pirate Planet.
Pg 258 "Yes, probably when I was with UNIT." Spearhead from Space et al.
Pg 271 "At 5:32 the chief engineer at Nunton tried to shut down the nuclear reactor when the computer predicted imminent containment failure." The Hand of Fear (and The Claws of Axos, almost).
Pg 278 "When did you last enjoy a meal or watch a sunrise?" Similar to what he later says in Earthshock.
Pg 305 "Ashley Chapel put in a bid for what's left, he won't be best pleased with the little you've left him." Millennial Rites.
Pg 309 "'Played hell with a friend of mine,' Sarah said." This is K9 (K9 and Company, The Five Doctors).
OLD FRIENDS AND OLD ENEMIES
NEW FRIENDS AND NEW ENEMIES
Robert Gibson (who returns briefly in Millennium Shock), Sergeant Collins, Greg Anderson, Duchess of Glastonbury, Colonel Clark.
Pg 162 Voracians, half humanoid, half cybernetic, with the organic part grafted on. The cybernetic half is snakelike, segmented and green, and they have thin forked tongues and reptilian skin. The other half is metal and plastic.