[spoiler alert - do not read if you intend to be a player in TERROR]
I always liked the TERROR scenario: the idea that players are being tested for their loyalty prior to being erased from the living and turned into special agents investigating the mythos that reaches into the very heart of the Soviet state has such pulpy overtones. but the scenario does not take this potential further (after all it's a one-shot) and instead drops it altogether by having the characters executed at the end. much worse, it suffers from so many historical inaccuracies that even players without much knowledge of the Soviet union would feel their suspension of disbelief breaking if it was played out as written.
what i set out to do was the following:
1) fix some of the historical mistakes and adjust the tone of some other scenes;
2) provide some historical background that can be used to add more realism to the setting;
3) integrate GRU SV8 into the narrative and set it up as a starting point for a campaign.
Most obviously, 1932 is not the time of the purges yet. However the terrain is being prepared and this is something the keeper can build on. Martemyan Ryutin was expelled from the party in 1930; he was released from prison in Jan 1931 and allowed to rejoin the party but remained in silent opposition to Stalin. He was allied with Nikolai Bukharin, a well-regarded figure in Soviet politics also opposed to Stalin. Bukharin confided to Lev Kamenev (another well-regarded Soviet revolutionary, former husband of Trotsky's sister Olga Kameneva) that Stalin was "Ghenghis Khan" and "evil genius of the Russian revolution". Bukharin, Kamenev and Zioviev lead a clandestine anti-Stalin platform, and Stalin is aware that this is the major threat to his leadership. Trotsky is more of a threat from the background - in 1932 he lives on Buyukada island in Turkey, thereby geographically still fairly close. So the atmosphere can be portrayed as politically ominous, and it is especially helpful to have one character who may be affiliated with Bukharin, Kamenev, Zinoviev and Ryutin.
The second problematic aspect is that the scenario assumes that the Tunguska explosion was common knowledge in 1908, so much so that the reports of a meteor in the swamp soon followed. In fact, the expeditions were only conducted in earnest at the end of the 1920s. In the scenario, Stalin is meant to have been imprisoned for revolutionary activities in the Krasnoyarsk region in 1912 and subjected to experiments with the meteor. For those who are familiar with Stalin's revolutionary years, this doesn't really fit in well. In Dec 1916 however, Stalin was made to travel to Achinsk (a place on the trans-siberian railway one mile from Karsnoyarsk) with assorted enemies of the state (including Kamenev) by dog sleigh. It makes sense to have Dr Chervyakov as a geneticist drafted as an army doctor who comes into possession of a piece of the meteor which at that point is used in witch-healing rituals by a local tribe, observes its mutagen properties, and commences on his own to conduct experiments on communist prisoners to learn more of its properties. This also allows a tie in with Kamenev: he can be involved into the story at a later point as he would presumably know about Stalin's strange experience with the meteor fragment.
The third problematic apsect is the timeline - if the meteor was so important, the cover up of the monstrous events in the wagon would be enacted very quickly. I pushed everything forward, so that the pick up of the meteor was on the day of arrival at 7pm, Berger stumbling onto the scene at 9pm (in a panic that ensued after the monster massacred the prisoners, the wagon was just closed and left unattended while the meteor was driven away) and the murder of Potakov and the start of an earnest cover up at 2am. The investigators have a window in which they can conduct some investigations at the wagon depo - after 2am, the wagon is taken away as if it was never there, Lupova gets murdered after speaking with them, the ominous black car (a NAMI-I) appears in front of buildings where important NPCs live and attempts to follow the investigators to their base. The recruitment of the investigators is orchestrated by Major Strudnikov of GRU-SV8 and comrade Rubeshkov is a friendly who fought with Strudnikov in the same unit and can be trusted. The investigators are given a disused building in Krasnoselski district to use as a base, as well as a car and some basic supplies. If the investigators manage to complete the mission but their base is discovered, the ending as written ensues, with the real OGPU waiting there for their report. If they manage to complete the mission without their base being discovered, they will be sent on the next mission for GRU-SV8.
There's also a few historical inaccuracies: the NKVD is called OGPU in 1932. Head of OGPU between July 1931 and Oct 1932 is Vyacheslav Rudolfovich Menzhinsky, although some say that his predecessor (and soon to be heir again) Henrik Yagoda is in fact in charge. Head of the anti-religious section of the OGPU is Yevgeniy Alexandrovich Tuchkov. The transport section is called GTU - Glavnoye transportnoye upravyenie. Together with the Narkomput it is in charge of transport, which is serious business: saboteurs on the railways are a big issue and are blamed on the worker-peasant party, industrial party and menysheviks. There are big tranport developments in Moscow itself - the plans for the underground have just been approved in Jan 1932. Metrovick (metropolitan-Vickers electrical company) from London is advising on the building, which leads to additional paranoia about foreign spying. Similar deals with the west were not unheard of in this period: e.g. in May 1929 a deal was signed with Ford to open the NAZ car factory, which duly happened in Jan 1932, with Ford's sign on the factory logo and its engineers contracted to provide advice. Mayor of Moscow (aka first secretary of Gorkom) at the time is Lazar Moyseyevich Kaganovich, with Nikita Kruschov as his deputy who is very much connected with the moscow underground project.
In terms of railway yards in Moscow, it is best to put them in Krasnoselski district, which contained multiple railway interchanges and stations (Yaroslavsk, Kazansk & Kursk stations) around Komsomolski square, where a big underground station will be built (to open in 1935).
Finally, in terms of Soviet science, in 1931 OGPU did purge a number of scientists. The academy of sciences itself is to relocate to Moscow from Leningrad in 1934. Soviet scientists have been known to indulge in a few wild projects and I envisioned Dr Chervyakov as a mad scientist whose experiments included production of the Soviet super-soldier by crossing gorillas and humans, with a Dr Demikhov-style monkey with two heads in one of the cages. I did not think it sensible that he should have a meteor thing captured in a cage - the way these things are described, they could easily break out of a cage at any time, and I thought it best if he had a dead meteor thing from M. Kalinin for autopsy. I think it also makes sense that if Dr Chervyakov is engaged in state sponsored top-secret experiments, his lab should be in a protected compound into which the investigators would need to sneak in or fast-talk their way through.
To follow this up, I plan to send the characters on a mission pursuing the Shokptsi who escaped to Shanghai from Vladivostok. That will give me the opportunity to use some of the marvelous material in the Masks of Nyarlatothep companion. Alternatively, tie ins would also be possible with Cold Harvest or MTS-37. I am not terribly fond of Secrets of the Kremlin, but it serves well as a prequel from the official DG:Countdown history for GRU-SV8, wherein it is said that in 1928 Stalin had found Ivan Grozny's secret library but that by April 1931 his experiments had failed. This presents a nice lead-in to him wanting to acquire the meteor fragment again.
Finally, no one should be called mister, as it says in the scenario, unless you're a pro-western subversive - it's for each comrade according to their needs, and from each comrade according to their abilities!