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.

After test screenings of the 120-minute version received unfavorable audience responses, the film was further truncated to its final 96-minute cut, which was released theatrically in December 1983.

In 1941 in Romania, following the commencement of Operation Barbarossa, a motorized Gebirgsjäger unit of the Wehrmacht, under the command of Captain Klaus Woermann, arrives at an uninhabited citadel – simply known as 'the Keep' – with the aim of taking control of the Dinu Pass in the Carpathian Mountains.

Two soldiers, privates Lutz and Anton, attempt to loot a metallic icon within the keep but accidentally unleash a spectral entity which kills them.

A detachment of SS Einsatzkommandos, under the command of sadistic SD Sturmbannführer Erich Kaempffer, arrives to deal with what is thought to be Soviet partisan activity in a nearby village.

At the instigation of the local village priest, Father Mihail Fonescu, the Germans retrieve an ailing Jewish historian, Theodore Cuza, from a concentration camp.

Molasar saves the professor's daughter, Eva, from sexual assault by two Einsatzkommandos and cures Cuza of his debilitating scleroderma by touch.

Having remotely sensed Molasar's presence, a mysterious stranger named Glaeken Trismegestus arrives from Axis-occupied Greece, seducing Eva and incurring Cuza's ire.

When their conversation is suddenly interrupted by the sound of horrible screams and machine-gun fire coming from the keep's inner courtyard, Woermann is shot and killed by Kaempffer.

Afterwards, Kaempffer goes to the now-silent courtyard, only to find that the entire garrison of the citadel has been slaughtered by Molasar, and that all the military vehicles parked inside have been disabled.

Writer Steven Rybin notes in his book Michael Mann: Crime Auteur that The Keep "does not construct a view of the world in which simple and unambiguous forces such as 'good' and 'evil' do battle.

[15] Mann ultimately settled on the entity initially appearing as an amorphous ball of energy which begins to take human shape with each appearance as the film progresses, morphing from a bundle of energy resembling a human nervous system, to a skeletal and then muscular form, and ultimately, a "statuesque Golem-like" body in the film's climax.

[15] A mechanical version of Molasar, which was designed early on during production, ultimately went unused due to Mann's shifting ideas about the monster's appearance, and instead the creature was portrayed by an actor in a bodysuit in its later humanoid stages.

These last-minute cuts resulted in many plot holes, continuity mistakes, very obvious "jumps" in soundtrack and scenes, and poor editing issues.

In July 2021, the score for The Keep was released on a standalone vinyl for Record Store Day by Universal Music Group's Canadian branch.

[30] Paramount released a theatrical trailer and television spots in promotion of the film, which include various footage from the extended versions of the film that do not appear in the final cut: Among them are a longer conversation between Woermann and Alexandru in which Woermann says that the keep looks like it was built to keep something in; a longer version of the scene where Molasar is talking with professor Cuza for the first time (also in this scene Cuza asks Molasar "What are you?"

[31] Although the film has been made available for purchase and/or streaming on YouTube, Amazon Video, Apple TV,[32] Criterion Channel (as part of the 80s Horror series[33][34]) and Netflix (UK and Ireland), it went unreleased in physical disc format (aside from LaserDisc) in any country until the Australian label Via Vision Entertainment released an official remastered DVD edition on 20 January 2020.

[38] Gene Siskel, film reviewer for the Chicago Tribune, rated The Keep two out of four stars, complaining that the Tangerine Dream soundtrack tended to overwhelm the dialogue.

"The Keep is the sort of movie I expect to see in one of the big cinema centres, being fed to the masses raised on Spielberg and spectacle", Eisenhuth wrote in her review.

[44] Michael Nordine of the LA Weekly wrote in a 2013 review that The Keep "can’t always keep its many moving parts in lockstep, what with its hinted-at mythos that obscures more than it elucidates and its cast of enigmatic characters whose precise dealings with one another are never made entirely clear".

[45] It has been mentioned that Michael Mann disowned the movie but in a 2009 interview he said that the production design and the form of the film were in better shape than the content, which is why he likes it for those aspects.