January, 1913, Cambridge.
G.H. Hardy - eccentric, charismatic and considered the greatest British mathematician of his age - receives a mysterious envelope covered with Indian stamps.

Inside he finds a rambling letter from a self-professed mathematical genius who claims to be on the brink of solving the most important mathematical problem of his time.

Hardy determines to learn more about this mysterious Indian clerk, Srinivasa Ramanujan, a decision that will profoundly affect not only his own life, and that of his friends, but the entire history of mathematics.