In a segregated city and time, two girls forge a friendship across social and physical barriers. The pair walk together through the changing world of Tulsa during the oil boom. Grace Irons struggles to root her changing friendship with white, outspoken Mercy Williams. When the girls discover a horrible secret, they cannot ignore their differences any longer. At a moment when their friendship is threatened, the girls witness the events that set Tulsa on fire in 1921. Will Grace and Mercy survive the seven days in May?