Which of these Alistair MacLean novels was not made into a Major motion picture?

The Alistair MacLean novels "The Guns of Navarone" (1957), "Ice station Zebra" (1963), and "Where Eagles Dare" (1966) were each used as the basis to make a major motion picture. The novel "Night Without End", a thriller by Scottish author MacLean, was first published in 1959. The idea to make it into a popular movie was proposed but never done.

The novel is one that is less well known, according to fans of MacLean, and perhaps this is why no film has been made. Nonetheless, "Night Without End" is a great thriller from a master storyteller. It is a mystery set in Greenland in December 1958 and tells the story of a disparate group of plane crash survivors in the bleak and dangerous Arctic. They seek help from the personnel at a scientific research base built for the year called the International Geophysical Year (July 1957 to December 1958), an international cooperative scientific program which was designed to study the earth and its environment. The base personnel happen to include a hero (who narrates the story) - cool, calm, collected and capable. This is just as well, because an investigation reveals that the pilot was shot before the crash - and he isn't the last fatality, as a ruthless killer among the survivors takes any action necessary to remain undetected. Who and why are the questions?

Respectively, film adaptations were made of "The Guns of Navarone", a 1961 war movie, "Ice Station Zebra", a 1968 espionage film, and "Where Eagles Dare", a 1968 WWII film.