In 1913, Srinivasa Ramanujan (Dev Patel), a self-taught mathematics genius from India, is invited to Trinity College, Cambridge by famed mathematician G.H. Hardy (Jeremy Irons). Upon arrival, he's met by Hardy's fellow mathmatician, John Edensor Littlewood (Toby Jones).
In class, when Ramanujan is unable to explain how he has arrived at his mathematical conclusions, he's treated with disdain and anger by his professors. When the stress of not being able to explain his theories, combined with the racism he experiences in Britain, becomes too much for him, the young man turns to Hardy, who stands up for the young genius.