Paul Schrader is back with his most successful picture since First Reformed in 2018. It’s a stereotypical Schrader study of masculinity in some ways, about a man agonising over moral choice and ethical behaviour while – as so often in Schrader’s movies – reading and writing philosophy in an austerely furnished room. And yet there is nothing abstract about the issue he faces here. The film moves with a determined suspenseful tread, everything hangs together right up to the queasy final shot and Schrader flavours everything with a streak of melodrama and even a kind of gaunt black comedy. Karl Glusman’s cameo is surely the weirdest thing at Venice this year.

The scene is a blandly prestigious liberal arts college, presided over by a genial, grey-haired dean, played in cameo by Richard Gere. John Jorrisen, played by Jack Huston, is the star of the philosophy faculty, enjoying agreeable mid-career success, working on a book about Spinoza. He is cordially resigned to bored students showing up to his “The Basics Of Philosophy” course for what they assume will be easy extra credit, attracted by that undemanding word “basic”.

But it is John’s task to show them that philosophy is basic, that all philosophy is philosophy 101, that the challenge is to recognise the primacy of moral simplicity over specious supposed difficulty. He is particularly exercised by the question of whether anyone can really change.

John is also dating a stylish colleague in the psychology department called Prof Rebecca Richards (Sofia Boutella), a single mum to whose 14-year-old son he shows every sign of becoming a conscientious stepdad. Yet something is wrong. John keeps taking Rebecca to unrelaxed formal restaurants and failing to stay over afterwards because he supposedly needs to work on his book on Spinoza – who is a stern moral presence. A mutinous student demanding a higher grade sneers that she knows “what he did”. Is she bluffing?

John’s growing malaise comes to a crisis with the death of his wealthy, overbearing father Melvyn (Bill Pullman) who abandoned his own dreams of studying philosophy in favour of a lucrative business career. He is seen in flashbacks which are in a soft black-and-white, perhaps partly to make it easier for Huston to play John’s much younger self: the late-teen-early-20s version.

John is astonished to see among the funeral congregation a certain man, Miguel Vasque (Daniel Zovatto), who is the key to his unease – and those concerned about spoilers should look away now. Miguel was the son of Melvyn’s gardener and when Miguel was the age Rebecca’s son is now, John sexually abused him; his father had to pay for Miguel’s private school and college education to cover it up – or, at all events, to make amends, as no one would believe Miguel’s word against Melvyn’s if it came to a police action.

John is horrified by the agonised dilemma which this has brought up. He has naturally convinced himself over the years that he is not of course a child abuser or a paedophile. But Schrader shows us how he may need to triangulate this self-image with the reality of his ongoing fear by telling himself that he simply does not fit into a heterosexual template; perhaps his sexual identity needs to be rethought, though this would of course be on a consenting legal basis. But is even that real?

And all the time he is digging himself deeper into a nightmare by reconnecting with Miguel. Could it be that he can make a grotesque kind of peace with his secret past by imagining himself in love with him? And he starts to ponder the awful final question that change might be impossible; if he is an abuser who will at some stage inevitably revert to type, then should he consider Socrates’ attitude to taking your own life, the coward’s or hero’s way out?

Schrader takes all this at a cool, cruel pace: the film has the thriller’s beady-eyed focus on what’s going to happen next, along with a dramatic sense of the perplexed inner man, the man who complacently thinks of himself as a philosopher, an intellectual who is detached from sordid faults, who has insight and perspective. And so he may indeed have, but they may be entirely irrelevant to his destiny. Schrader takes us to an elegant, indirectly macabre finale; this is a very disquieting portrait.