“Cold Case Hammarskjöld” is a documentary about the death of U.N. General Secretary Dag Hammarskjöld, whose airplane crashed in Northern Rhodesia in 1961. The plane was believed to have been shot down by a Belgian-British mercenary pilot. But new evidence suggests the assassination is just the beginning of a story involving the CIA, MI-6, and an extremist cover-up. “Cold Case Hammarskjöld” will definitely keep you guessing up until the end. — Charlie Brown Sanders