The Keep is a 1983 supernatural horror film written and directed by Michael Mann and starring Scott Glenn, Gabriel Byrne, Jürgen Prochnow, Alberta Watson, and Ian McKellen. Set in Romania during World War II, it follows a group of Nazi soldiers who unleash a malevolent supernatural force after setting up camp in an ancient stone fortress in the Carpathian Mountains. It is an adaptation of the 1981 novel of the same title by American writer F. Paul Wilson. The musical score was composed by Tangerine Dream.