NOMISYRRUC, please, could you start a separate thread ? My POD is much later than yours.
Athelstane, I have a funny twist to add to our story. Imagine that Leonov and Makarov, when they circle the Moon in March 1969, don't die. Instead their Zond land, but miss its skip reentry like Zond 4. Well, Zond 4 was destroyed over the gulf of Guinea because it apears it would land in China.
Some Soyuz (and Zond) landed in Mongolia. Next to Mongolia is China most northern area - Harbin and the like. If the rocket fail a little later, Soyuz or Zond may well overtake both Kazakhstan and Mongolia and land there. Zhenbao island is not too far away.
In March 1969 the Soviet and Chinese clashed over Zhenbao island. Imagine the mess if Leonov and Makarov landed there... if they were taken priosniers by the Chinese. Could that be a casus belli and trigger WWIII, or even a nuclear exchange ?
This came up in Red Star as well.
I'd think insofar as Mao is in control, he would enjoy humiliating the Soviets but would hold the cosmonauts only briefly--just long enough to put a scare into them and into the Kremlin; then, with much show and fanfare, return them to the USSR.
I'm ambivalent about whether he'd have the gall to keep the return capsule as spoils of severe ideological conflict verging on war, or return it too.
The tricky bit is that by 1968 IIRC the Cultural Revolution is in full swing and Red Guards (who believe they are doing Mao's will) are all over the place. It is conceivable that some of them would be so overzealous as to do something irrevocable to one or both the cosmonauts. Mao would have to put the best face on it he could--from the point of view of his political priorities that is; this early in the CR he'd hardly want to take the wind out of the Red Guards' sails so he'd probably back their play and present whatever they'd done as inevitable and just.
But behind the scenes I'd think he'd be pulling strings to keep them safe (if not necessarily comfortable, and frightened would be just fine) to return them intact because he'd understand that on the world stage that is the sensible thing to do. We know Mao launched the CR and unleashed the Red Guards in the first place and is keen to avoid the appearance of China being beholden to any foreign power, be it Moscow or the West. But we also know that OTL he was not above responding to Nixon's overtures toward diplomatic normalization; I'd think therefore he (and a large faction of the CCP leadership with him) would want to put themselves in a good light vis a vis general world opinion; returning the castaways alive and in good condition, after a brief delay to demonstrate they aren't doing it under duress, is the obvious thing to do.
The RGs might screw it all up of course. But I'd think they'd await orders from Beijing before doing anything irrevocable.