Fitz is under interrogation regarding a burglary and fire at the Kremlin... where the Doctor disappeared in the flames.
Fitz and Trix.
Pg 12 The TARDIS has materialised in the Kremlin armoury before the story began.
Pgs 176/178 Russia, September 2, 1812.
Pgs 200/201 Paraiso (although the TARDIS materialises between scenes).
Pg 241 Garudin's laboratory, 2024.
Pg 265 Siberia, 1812 (although the TARDIS materialises between scenes).
Pg 274 Paraiso (although the TARDIS materialises between scenes).
The Talons of Weng-Chiang might be helpful, but isn't essential.
Pg 33 "Ogron?" Not, it turns out, the aliens from Day of the Daleks and Frontier in Space, but rather a Russian organisation.
"You read Cyrillic?" Trix's familiarity with the Russian language was seen in Time Zero.
Reference to UNIT. You know who they are.
Pg 75 "She and fellow students had fled west, driven by the advance of the PacBloc forces and stories of Mogushestvo and Greel" The Talons of Weng-Chiang.
Pg 77 "Greel may have retreated to China" The Talons of Weng-Chiang.
Pg 86 "I don't know nearly enough about Zygma energies." The Talons of Weng-Chiang.
Pg 107 "I'll not have another one slip away like Greel." The Talons of Weng-Chiang.
Pg 148 "From Magnus Greel. The Butcher of Brisbane" The Talons of Weng-Chiang. Also, the Doctor doesn't recognise the name here, thanks to his amnesia from The Ancestor Cell.
Pg 149 "What is important is that he was engaged in research into Zygma technology" The Talons of Weng-Chiang.
Pg 197 "Greel, no less." The Talons of Weng-Chiang.
Pg 211 "To Fitz, it sounded too much like Meet me in St Louis." The Ancestor Cell, Escape Velocity.
Pg 228 "Another mutant brainchild of Greel's" The Talons of Weng-Chiang.
Pgs 228/229 "The weapon is some sort of psionic device, designed for subversion. [...] The weapon, smooth and ebony black, nested in a delicate cradle in the centre of the cryo-locker" This is the same weapon that finds its way back to 1933 in Eater of Wasps.
Pg 236 "Confronted with this world, Fitz's memories of Siberia were almost a comfort." Time Zero.
Pg 247 "'Yeah, one more trip to Siberia.' Fitz gave a weak imitation of a laugh." Time Zero.
Pg 252 "Mogushestvo was no Greel, he was no god" The Talons of Weng-Chiang.
Pg 270 "There's no telling what damage Greel's experiments might have done to the timelines. Perhaps my temporal paratroopers are best developed into a unit for policing the past and preserving the future." The Talons of Weng-Chiang. These presumably become the time agents Greel refers to in that story, of which Captain Jack Harkness was a member (The Empty Child/The Doctor Dances).
Pg 273 "'A crystal, with a wonky kite design imprinted on its structure at a molecular level. The same one we found on a book.' A cross-section, the Doctor had pointed out again, of a diamond." Timeless.
OLD FRIENDS AND OLD ENEMIES
The Icelandic Alliance appearing here was mentioned in The Talons of Weng-Chiang.
Napoleon appears briefly on page 237 (he also appeared in The Reign of Terror and The Sands of Time and later appears in World Game).
NEW FRIENDS AND NEW ENEMIES
Dusha Vishenkova, Razum Kinzhal, Natasha Vishenkova, Irena Vishenkova, Count Yuri Vishenkov (Papa), Colonel Bugayev, Tatyana, Aphrodite Diamante.