The poisoning plot seemed right out of a Russian playbook. An unhinged and vengeful chief of state, obsessed with historic grievances and destroying enemies. Obsequious apparatchiks slavishly devoted to following orders. Intelligence operatives trained in assassination techniques and eager to carry them out.

But this conspiracy to execute an investigative reporter took place not in Moscow, but in Washington. The head of state wasn’t Vladimir Putin; it was Richard M. Nixon. The plot was hatched 50 years ago this week, although the story has largely been lost to history.