Dr. P. P. Humayan expects prejudice from the English. Growing up in Bombay, he was raised on stories of the injustices of life in Britain, where racial status is marked on one's papers and anyone of Celtic descent is born with green skin and forced to live in walled-off ghettos. But when he travels to London to announce that he has solved the genetic mystery of why the Celts are born green, he is shocked by the system's brutality. Only one English girl is kind to him--and she will soon find herself in mortal peril.

When his host family is murdered, Humayan slips underground, joining a small band of rebels who would do anything to see racial equality restored to England. There are powerful men working to maintain the sinister status quo, and bringing them down will be the toughest problem this mathematician has ever faced.