It's the late 1970s, Mao is dead, and tensions are rising between the USSR and China. The US is set on a policy of detente, and doesn't want war between the two major communist powers--especially not a nuclear exchange. The cloud of radioactive fallout would reach the west coast of the US, with potentially major consequences.
The current Communist Party Chairman, Dimitrov, has convinced the President and the Secretary of State that he agrees with him and is the safeguard against a disastrous war. Unfortunately, he has leukemia, and is dying.
The US secretly agrees to send one of the world's leading leukemia experts, fortunately the son and grandson of Russian immigrants and a speaker of Russian, to treat Dimitrov and hopefully keep him alive long enough to attend an international meeting and sign a treaty.
Dr. Alex Cousins, né Kuznetsov, is off on an adventure he never expected or wanted.
It's not too bad at first, treating Dimitrov successfully and bringing him back to greater health, at least for now. But along the way, he learns a dangerous secret about Dimitrov's real plans for China. When it's time to go home, Alex finds himself being given the "gift" of a trip on the Trans-Siberian Express, through Siberia where both his father and grandfather spent important years of their lives, culminating in theory in a boat ride to Yokohama and a plane trip home.
Alex doesn't believe he'll ever make it, unless he can find a way to get his dangerous message to US authorities before he's stopped.
Along the way, we see both the grimness of the Soviet system, and glimpses of what the Russians, especially the Siberians, love about their country. A beautiful Russian history professor, recruited back into KGB employment she left ten years ago, Dimitrov's hatchet man Zeldovich, assorted other KGB agents, a carload full of KGB soldiers, and even the railroad steward staff are all either really watching Alex, or making him feel that they are. The deeper they get into Siberia, the more events and misunderstandings and all too real conflicts ratchet up the tension and the danger.
This is a very solid political thriller set in a half-forgotten period of our recent history, when the collapse of the Soviet Union was still unthinkable, and Mutual Assured Destruction was what was keeping us all alive.