Dramatization of the real-life romance between white Londoner Ruth Williams (Rosamund Pike) and African law student Seretse Khama (David Oyelowo), who began their love affair in 1947 when Williams was unaware that Khama was the heir apparent to the throne of the Bamangwato tribe of the British protectorate of Bechuanaland (modern-day Botswana). After deciding to marry, the couple return to Africa so he can assume his royal duties, but their interracial marriage faces opposition from both Khama's family and neighboring South Africa, whose apartheid government leans on Britain to break up their union.