It is 1979. The first Commonwealth Heads of Government Summit on African soil is due to take place in Zambia, and graced by Queen Elizabeth herself. Barely a week before this much anticipated event, a white British couple, Henry and Laura Hinckley, are brutally killed on their farm on the outskirts of the capital city, Lusaka. The unknown perpetrators are at large, their motive unclear. Fearing a media backlash, the British government applies pressure on the Zambian authorities to bring the culprits to book, threatening to cancel the Queen's trip altogether.