Young British miner Harry Speares is no admirer of Josef Stalin.
But when, in the late 1930s, his communist father Joseph is invited to work at the headquarters of Moscow's global subversive network, the Comintern, he reluctantly accompanies him - lured by promises of an education denied him at home.
In the Hotel Lux, foreign communist leaders live alongside exiled revolutionary fighters, teachers, writers and spies. Here, Harry meets Rosa Zander, a beguiling German woman who verses him in the mysterious rites of his new home. Rooms hum with debate, laughter and music. Children play in the corridors. But for Harry, the outsider, there is something unsettling about those 'believers' so set on remaking the world.
As the threat from Nazi Germany escalates, Stalin turns against his loyal servants in the Lux. Rosa struggles to explain a bloody betrayal that bewilders and infuriates Harry. But Harry's fascination with her grows, along with his fear of her power, as she draws him into the darker corners of the Comintern. Is she friend, sweetheart or jailer? Desperate to escape Russia, Harry embarks on a perilous journey into Moscow's criminal underworld that leads him to the gates of the British Embassy. Where he goes, Rosa follows.