There are traumatised central figures in both films (Dorothy McGuire as Helen in The Spiral Staircase, unable to speak, and James Stewart's Scottie in Vertigo, terrified of heights) who, at the end of the films, are left cured in the ruins of everything they have known. There is much emphasis on the ambiguity of seeing, complete with extreme close-ups of watching eyes, prying but also trapped, unable to look away. Roy Webb's music for The Spiral Staircase gives way at heightened moments to the spooky, muffled shriek of the theremin, just as Bernard Herrmann's score for Vertigo, famous for its recycling of Wagnerian love-death, also features sustained high trills on the electric organ, the quintessential sound of 1950s cheesy menace.
The difference is between a thriller that hardly bothers to thrill but has an extraordinary ability to haunt, and a genre product that touches all the bases without leaving any more to trouble the memory, perhaps, than a single image. Everyone seems to have noticed the singularity of Vertigo, including its unenthusiastic original audiences, who did not want to have their sensibilities extended in this sombre fashion. No previous film made by a Hollywood studio had dared to enrich a second viewing, at the expense of a first, by revealing the plot's secret so early.
Yet The Spiral Staircase could just as easily be said to have personal elements. Siodmak brought with him from Germany not only a distinctive approach to cinematic lighting and composition but, as a Jewish refugee from Nazism, a certain amount of experience of the ideology of the murderer in the film. In Mel Dinelli's script, adapting a novel by Ethel Lina White, the victims are all in some way disabled, and their killer makes it clear that he is ridding the world of weakness and imperfection (in a posthumous attempt to impress his proto-fascist father).
The heroine's defect is an inability to speak out. Helen's attempts to find her voice, though, to break her silence, have to do mainly with the need to say "I do" to the nice doctor who's taken such an interest in her, and these sequences are very mildly nightmarish compared to the film's single truly memorable shot. The heroine is mouthing words in the landing mirror while the killer spies on her, and we see her as he does, with a gauzy blur where her mouth should be.
This subjective shot in the film's first half hour brings us closer to the murderer, for a moment of jolting complicity, than we ever are to the heroine, despite our routine identification with her. Yet Siodmak goes no further in this line, and perhaps for that reason falls short of achievements of pre-war German cinema such as Fritz Lang's M, where the psychology of monstrousness isn't so disappointingly shelved.
If evenness of tone were a pre-requirement for masterpiece status, then Vertigo would be a non-starter. There is nothing in The Spiral Staircase as hopelessly misjudged as the nightmare sequence. James Stewart's face on his pillow is bathed in a series of lurid colours, then we see the bouquet carried by the enigmatic Carlotta Valdez coming to feebly animated life (this, presumably, is the "special sequence" credited to John Ferren), and we're off on a clanking roller-coaster of back projections and stubbornly uncontagious terror. Perhaps the original 20-minute dream sequence, designed by Salvador Dali and shot for Hitchcock's Spellbound, wasn't the great loss it has always seemed.
The script, by Alec Coppel and Samuel Taylor, transforming a French source novel and transplanting it securely to San Francisco, has its own preposterous logic, but a script editor might have pointed out that if you cast youthful Barbara Bel Geddes as Scottie's loyal not-quite-girlfriend Midge, then you have to eliminate the bit of dialogue that makes them college sweethearts. Other oddities are clearly intentional, even when slightly baffling: now that the film has been so comprehensively restored, audiences must just accept that the light is supposed to drain greenishly away in the course of a bookshop scene where the story of Carlotta Valdez is rehearsed for the first time.
Vertigo has been an astonishingly influential film. Its themes of repetition and compulsive romanticism, its lush bleakness or bleak lushness, have inspired paraphrases such as Brian de Palma's Obsession (1975), and Jonathan Demme's Last Embrace (1979), where at least the female lead was as ambiguous as the male, and Janet Margolin got to express the range of emotion denied to Kim Novak in the original. The shot devised by Hitchcock for the film and named after it, combining a zoom in and a tracking shot out, leads it own independent life, appropriated and parodied in all sorts of contexts. It provides the single most powerful moment in Jaws (a reaction shot of Roy Scheider on the beach); it introduces the heroine in the Jim Carrey vehicle The Mask. Yet the "Vertigo shot" in Vertigo itself is used rather flatly and repetitiously. It happens rather quickly, for one thing, with the ground dropping away rather than sliding, so that it seems to convey the simple fear of falling rather than a more complex state of terror and longing.
It's different with the film's other customised shot, the kiss across time, in which Scottie, embracing one woman while the camera revolves around them, seems to return to the place where he first kissed another. Hitchcock is more sparing with this even more powerful effect, which seems to convey the disorientation of fulfilment, the subtle terror that you'll have to think of what to do next, what to want next, now that you've got what you set your heart on. It doesn't damage this moment to know that the actors were on a turntable - nor even to realise that the same shot is used on television, most nights, to sell an Irish beer.
'Vertigo' from tomorrow at the West End Lumiere, London WC2 (0171-379 3014); 'The Spiral Staircase' in rep from tomorrow at the NFT, London SE1 (0171-928 3232)