The film is based on a 1981 novel by New Jersey doctor F. Paul Wilson, a minor writer of some passable horror and sf novels. After the book became a best-seller, the film adaptation was taken over by Michael Mann. At the time, Mann had begun working as a writer and later director on 1970s tv cop shows such as Police Story (1973-7), Police Woman (1974-8), Starsky and Hutch (1975-9) and had created the tv series Vega$ (1978-81). Mann made his directorial debut with the worthwhile but little seen Thief/Violent Streets (1981), which defined the cool, moody, Euro-styled crime thriller that Mann has become most associated with. Subsequent to The Keep, Mann made the first Hannibal Lecter film Manhunter (1986) and then created the quintessential 1980s cop show Miami Vice (1984-9). Miami Vice represented the essence of the Mann style shot in evocative washes of primary colour, amid often stylised sets set dressed with a bare minimalism, the ambient soulnessness of electronic music (frequently German group Tangerine Dream) on the soundtrack, and the moody quest for interior spaces. Despite the No. 1 hit of Miami Vice, neither The Keep nor Manhunter were successes in theatres and Mann was subsequently stuck in tv land, producing shows like Crime Story (1986-8) and various mini-series. It was not until the 1990s that Mann returned to the directors chair with The Last of the Mohicans (1992) and then wowed everybody with Heat (1995) before moving onto his epic canvas true-life dramas and award-friendly favourites such as The Insider (1999), Ali (2001) and Public Enemies (2009) and subsequent crime thrillers like Collateral (2004), Miami Vice (2006) and Blackhat (2015). Michael Manns one other genre credit is as a producer of Hancock (2008), which he was once slated to direct.
As a film, The Keep feels torn between two camps. It feels like it is stuck aground unable to find a common place between the stylish arthouse chic of director Michael Mann and the pulp horror elements of F. Paul Wilsons novel. It is clearly the ideological scope of the novel that attracted Michael Mann, not the horror element. What we end up with is another case of filmmakers with artistic pretensions being afraid of horror Mann seems only interested in the Molasar as metaphor for Nazi evil and has gone even so far in the film as to divorce any of the implications that The Molasar was a vampire that Wilson gave us in his book.
As a horror film, Michael Mann crucially never digs his teeth into the audience, never evokes any sense of dread during The Molasars appearances. There are a couple of frissons to the first attack, and the creatures rescue of Alberta Watson is genuinely unearthly. However, rather than devouring his victims, all the Molasar does is seem to emerge in laser light effects and mist with glowing red eyes. Certainly, the ideas inherent in F. Paul Wilsons somewhat pulpish novel find a better airing here than on the page there is that great moment where the Molasar steps up to Gabriel Byrnes SS commandant, effortlessly crushing his crucifix, Where am I from? I am from you.
If looks alone could make a horror film, then The Keep would be a classic. Michael Mann uses the oppressiveness of white-on-white walls and the dank grey-black of the perpetually mist-layered keep in the same way that an impressionist uses watercolours. The stone and narrow hallway sets are stunning and the way that Mann creeps the camera through in dreamy slow-motion to the metallic tappings of Tangerine Dreams electronics creates a great deal of atmosphere. Even the love scenes are something ritualised, not of this world. Regrettably the arty pretensions get the better of Michael Mann during the latter half of the film with the blank-faced Scott Glenn in purple contact lenses and talking as though with a mouthful of marbles, giving the most laughably daft performance of his life, and a climax that is pretty but meaningless Spielberg light effects. It is lamentable that the care Michael Mann languished on the film he proudly spoke in interviews of how dialogue coaches were obtained to get the regional inflections of each characters dialogue down pat, and how the WWII military hardware was authentic could not have been spent on producing less artful and more impact-ful scares. There are fair performances from Jurgen Prochnow, a then unknown Ian McKellen and the beautiful Alberta Watson, but as characters they seem swallowed up by one directors fascination with mood almost to the exclusion of all else.
F. Paul Wilson has later expanded the basics of The Keep into a six-volume series of novels. The concept of German soldiers facing supernatural evil in a claustrophobic space was later used with much greater horror effect in the British-made The Bunker (2001) and the New Zealand film The Devils Rock (2011), while the basics were transplanted amid US soldiers in contemporary Afghanistan in Red Sands (2009).