When JBS Haldane died in 1964, in Bhubhaneswar, he was an Indian scientist. He had the passport, but he also had a deep and abiding love for the country. His move to India was the final act in the boisterous life of Haldane, a geneticist, a staunch Communist and an all-round rabble-rouser. This story of a man who wrote his first scientific paper in the trenches of the First World War; who was a card-carrying member of the Communist Party; who went to Spain to fight the Fascists during the civil war; who was under heavy suspicion of being a spy for the Soviets; who courted trouble and ticked off the establishment repeatedly. Haldane's contributions to genetics are singular, and in tandem with his Communist beliefs, they make us think about how science and politics intersect, and how genetics continues to throw up great ethical and political conundrums today, as it did in Haldane's time.