The true story behind Leonardo DiCaprio's latest epic Killers of the Flower Moon

In the town of Fairfax, Oklahoma, the fact that life was good for the Osage Indians in the late 1800s might have seemed to some like sweet justice. 

For the reservation they had been shunted to decades earlier had turned out to be brimming with oil, and the tribe put it good use by building mansions, buying cars and sending their children to private schools.

But, by the time the 1920s came around, at least two dozen of them had been murdered by being shot, poisoned and blown up - and...