This based on Daphne Du Maurier's story famous metaphysical thriller postulates charming hypothesis that in this world nothing is accidental, and there exists inconceivable for mere mortal's mind "pattern" of every human life. Without any attempts of interpretation Roeg uses only cinematic images and means to show viewer (all-seeing but unable to meddle observer) one of those patterns. This is a puzzle that can be assembled but its real meaning is incomprehensible for us. Despite cold severity of the plot the film is not pessimistic: it tells us that our beloved people are mortal but if the pattern of every life exists and if surrounding symbols aren't phantom then nothing disappears forever and nothing passes away tracklessly.
It's worth to mention that apart from its metaphysical secrets film suggests for viewers and more simple and traditional pleasures: e.g. marvellous athmosphere of winter everyday Venice without tourists. Laconicism of the plot turned out to be an interesting effect: it seems to viewer as if the whole empty city existed especially for married couple and everything in it was related with their tragedy and their attempts of the return to the life. Local athmosphere rarely in cinema becomes such essential part of the story: Roeg's Venice is a part of that inconceivable weird world.9/10