The Trouble With Harry is Hitchcock’s most experimental, subversive and uncompromisingly strange black comedy – about people in a small town who can’t decide what to do with a dead body – was a catastrophic commercial failure. It lost half a million dollars at the box office and was unavailable for decades after release. Hitchcock wryly called his box-office flop an “expensive self-indulgence”; to Truffaut, he said that “the humour is quite rich”.

It was adapted from a novella by British author Jack Trevor Story, by one of Hitchcock’s favoured screenwriters, John Michael Hayes (Rear Window, To Catch a Thief, The Man Who Knew Too Much). The action was transplanted from its original English countryside setting to a folksy, gently autumnal Vermont. It begins with a scene of intense, captivating strangeness. A little boy runs through woodland with a toy gun and, in a world of his own, pretends to fire it. He then freezes rigid, terrified, on hearing real gunfire. It is the only time in the movie that anyone looks scared. Are real grownups firing back at him? Has he somehow magicked them into being? All the while Bernard Herrmann’s unsettling score offers premonitions of his Psycho theme. The boy hears shouts in the undergrowth, and then finds a man’s dead body with blood trickling from what looks like a bullet hole in the head.

But wait. The body isn’t sprawled on the ground, arms and legs flung wide, the way it surely would be in an undisturbed crime scene. It is stretched out, neat and proper, as though laid in an invisible coffin, with polished shoes and a slightly dandyish suit and tie. Twice, Hitchcock gives us the foreshortened camera angle with the kid looking down the length of the corpse, and it looks as if the great big feet are protruding from his little frame.

Subsequent events show that a number of people have a reason to feel uneasy (the word “guilty” isn’t quite right) about the deceased, whose name turns out to be Harry Worp. There is Jennifer, played by Shirley Maclaine in her first movie role, a pretty young widow, mother of the little boy. There is the roguish retired sea captain, Wiles (Edmund Gwenn); Mildred Natwick, a John Ford regular, plays the simpering spinster Miss Gravely with whom Captain Wiles is enamoured. John Forsythe (who as a silver-haired older man would later find fame as Blake Carrington in the 80s TV soap Dynasty) gives a laconic, Bogartian performance as a handsome artist called Sam Marlow who falls in love with Jennifer.

Each of them prods the corpse, or frowns at it, or sighs over it, or worries that it will cause trouble – or, in Jennifer’s case, laughs with unfeigned relief and delight at the sight of it. (That nice Shirley Maclaine!) But nobody goes into shock and astonishment and immediately calls the cops, the way they would in real life, or in a conventional movie. A conventional movie would introduce a police inspector, who would interrogate all these people, and their connections with the deceased would be made apparent to the audience that way.

Not here. Eerily, weirdly, each character is basically unconcerned about that most horrible of things, a dead body. They discuss having tea over the body. They discuss their love lives over the body. (Very recent attempts at assault and rape are remembered with a detached smile.) Jennifer giggles heartlessly; Sam draws the cadaver. Are they all monsters, or suffering from mass psychosis? No. Hitchcock’s genius is to keep strictly to the bad-dream logic. These are all nice people in a silly spot of bother. They walk and talk and move around the screen like lucid somnambulists.

What Hitchcock did in The Trouble With Harry was to remove the suspense: an extraordinary act of formal daring. (His Rope, made in 1948, centred around a dead body, too, but here there was a far greater sense of suspense: the two students are desperate that the body concealed in their flat remains a secret.) In Harry, even the arrival of the deputy sheriff and the doctor in the final scene is not suspenseful or climactic: more a woozy, bizarre comedy starring people who look like human beings but aren’t. They should be astonished at the body in the bath; they are perplexed but calm.

Is Hitchcock, in fact, tipping us a sly wink with Sam, the misunderstood artist whose modern experimental canvases are sold by the local postmistress? She hangs one the wrong way up. With an indulgent chuckle, Sam turns it the right way round – but isn’t the least bit cross. At the time, no one knew which way up to hang The Trouble With Harry. It’s time to take another look.