Ignored by history for 40 years, the Oversteegen sisters’ true story inspires “Murderers” (1941-1990). Two teenage girls lure a Nazi to his death. Echoing the psychological trauma of war, emigration, and today’s chilling winds of fascism, the film asks: what is the true price of murder for a righteous cause, and what remains of our humanity after we are forced to cross the ultimate line?