A Different Loyalty (2004) on Netflix

Plot summary

Sally Cauffield, an American and a former art consultant, has been married to the British journalist Leo Cauffield for four years. They live in Beirut with her teenage daughter Jen Tyler and his teenage children Lucy and Oliver. Leo once ran counterintelligence at MI6; he was asked to resign when several Cambridge recruits of his generation were found to be Soviet spies, though his name was cleared. Andrew Darcy, his best friend, still works at MI6, and Leo has been asked to rejoin, though he has not accepted. One morning Leo leaves for work and does not come back. Sally receives handwritten letters from him saying he is all right and will explain in time. Then MI6 tells her they believe Leo has defected to the Soviet Union. Sally must decide whether to travel to Moscow to look for him.