During WW2, a detachment of the German army (commanded by Jurgen Prochnow) is sent to guard a mysterious Romanian keep located on a strategic mountain pass in Carpathian Alps . The Nazis ignore villagers' warnings and of a Orthodox monk (Robert Prosky) about a weird presence inside. But one of the soldiers unwittingly releases an unknown spirit trapped within the walls. As the soldiers are mysteriously killed, the SS (Gabriel Byrne) arrives to deal with what is thought to be partisan activity. What the SS encounters, however, is an evil force trapped within the citadel, a menace that will do anything to escape its prison. At the point of desperation, the Nazis have no choice but to seek the aid of a Jewish man (Ian McKellen) and his daughter (Alberta Watson), who are both knowledgeable about the keep and who can translate signs vital to combating the rare menace . Meanwhile appears a strange man (Scott Glenn) with supernatural power, an angel exterminator named Glaeken.

The Keep is based on the novel by Paul Wilson who adapted it for the screen along with director Michael Mann. There are several different versions floating around which include different endings and additional footage. The star-studded cast is well headed by Jurgen Prochnow, Scott Glenn and Ian McKellen and excellent plethora of secondaries such as Gabriel Byrne, Robert Prosky, William Morgan Sheppard and a very secondary role by Bruce Payne and Roselie Crutchley. Impressive production design with some truly breathtaking scenes by John Box. Colorful cinematography with fog and fume and plenty of light and shadows by Alex Thomson. Tangerine Dream (Christopher Frank, among others) is on hand to provide an eerie musical score that compliments the visuals perfectly. The story will appeal to terror genre fans and WWII buffs.