The 1958 version of The Fly, screenplay written by James Clavell, opens with title and credits shown over a screen with a small hole. We zoom in progressively until the hole fills the screen and a fly crawls into frame.
The opening scene is at night, outside the factory of Delambre Freres Electronics in Montreal. A cat, Satan, is picked up by the night watchman, Gaston. He starts his rounds. He hears the sound of a hydraulic press starting. Gaston sees a smartly dressed woman, who he later recognizes as Helene Delambre, stare at him in surprise. She runs away.
He approaches the press and notices, in horror, that it is covered in blood. A body lays crumpled on the floor next to the press. He recoils in horror and screams. A phone rings in the home office of Francois Delambre. His sister-in-law, Helene, is calling. She calmly tells him, "Francois, I've killed Andre. I need your help."
Francois thinks it is a cruel joke but changes his mind when Helene breaks down sobbing and implores him to, "Call the police and come quickly." Before he can leave his office, there is another call, this time from Gaston at the factory. Gaston reports a murder. Francois calls an acquaintance at the Anthenium Club, a fellow member, Inspector Charas.
He reports the crime, then waits for Charas to collect him at his home. As Charas and the police examine the crime scene, an ambulance team collects Andre's body. Francois raises the press so what is left of the body can be removed. It is noted that the press was set to zero and single strokes. Francois positively identifies his brother based on a scar on his left leg--war wound. Francois is baffled by the crime.
Francois and Charas go to see Helene at home. Emma, the housekeeper, meets them at the door. Dr. Ejoute, the family doctor, reports that she is calm and admitted to the crime. They enter the living room to confront Helene Delambre. She is very calm and volunteers, "I killed my husband, Andre Delambre, about half an hour ago in the hydraulic press shed."
She admits to killing him, but when asked why she is adamant, "I cannot answer that question." She provides specific details of the crime, then offers Charas coffee. She is polite and answers all questions except one--WHY. She hears the buzz of a fly in the room. She gets up and searches for it. She registers relief when she finds it on a lampshade and it is only an ordinary fly.
She returns to the couch and more questions from Charas. Charas makes arrangements with the doctor to provide a police nurse to attend to Helene. Before he leaves, Charas asks Francois to show him the lab. Francois discovers the lab a shambles. Charas tells Francois that he is baffled and, "There appears to be no motive, no reason except insanity."
Charas suggests Francois take charge of his nephew for the time being. The police nurse, Andersone (Betty Lou Gerson) brings Helene her lunch, then takes her pulse. She sits and occupies her time with her reports and needlepoint. Helene makes a point to mention her son, but pretends she does not know him. The nurse registers mild surprise, then makes a note on the chart.
Helen starts eating, then stops when she hears a fly buzzing in the room. The nurse bats at it, much to Helene's shock and concern. The nurse rolls up a newspaper and chases it around the room. She becomes hysterical when the nurse swats it by the window. Helene collapses and is helped back to bed sobbing. The nurse collects the dead insect and gives it to Charas.
Charas asks Francois, "Mr. Delambre, do you think shes mad?" "It's obvious, isn't it?" is the reply, but Charas surprises Francois with his conclusion. "In spite of what the doctors think. I believe Mrs. Delambre's mind is quite clear. Even when catching flies." Charas intends to charge Helene with murder, the warrant will be issued the next day.
Francois is having dinner with his nephew, Philippe. When asked about the life expectancy of flies, Francois responds that he doesn't know. Philippe volunteers that he found the special fly his mother was looking for--one with a white head and leg. The discussion intrigues Francois, especially the mention of it being in his study. He calls Charas, but decides not to talk to him.
He goes to his brother's house, and lies to the nurse to secure a visit with Helene. He convinces Helene he has the special fly and wants the whole story. He finally convinces her to come clean, but before she recounts the tale she insists Charas be present. She demands Francois promise to kill the fly he claims he has. Charas arrives and she tells her story.
It started a few months earlier. She and her son are playing in the living room when her husband, Andre appears. While Philippe plays with the family cat, Dandelo, Andre and Helene go to the basement lab. Andre proudly shows her all the new equipment. He demands secrecy, then shows her his new line of research.
He places an ugly green plate, a wedding present, in a glass and metal container. He fires up the machine. The room goes dark, and the container glows a bright blue, then a flash of light and the equipment powers down. Helene is surprised by an empty container. They walk to another room and the plate is now in an identical container. Andre explains the concept to his disbelieving wife.
She chuckles, noticing that the matter transference device has one little flaw. Helene points out the "Made in Japan" stamp on the bottom of the plate is mirror-imaged. Andre returns to his desk and begins a review of his work. He recalculates, rechecks and retests. This time with a newspaper, the transfer is successful. Andre decides to run a test with the family cat, Dandelo.
The saucer of milk transfers fine, but to his horror the cat fails to appear. He hears only the plaintive echo of the cat's cries in the room. Helene is preparing to go out for the evening. Andre appears. He has been busy in the lab for weeks and insists they go out to celebrate. They return to the lab very late and Andre shows his wife the improvements he has made to the equipment by transferring a bottle of champagne.
The label is perfect and the wine is still cold. He then transfers a guinea pig, against his wife's objections. The animal appears fine after re-integration. Andre confesses that his first live animal experiment, Dandelo, was not successful. Helene expresses her concern about the technology, "It's frightening. It's like playing God." It has been a month and the guinea pig is fine. Andre is relaxing out in the garden.
Helene joins him. She tells Andre that Francois is coming to lunch. Andre is excited and tells his wife, "Bring him down to the lab. We'll show him now." Francois and Helene go down stairs to the lab, but encounter a note on the locked door instead of a welcome inside. It says, "I am working. Do not Disturb." Francois comments about the bad penmanship. Philippe enters the house.
He excitedly tells his mom, "I caught such a funny-looking fly. You want to see it? It has a funny white head and sort of white leg." His mother tells him to let it go at once. A report from Emma about Andre not touching his dinner does not alarm Helene. She walks down to the lab to check on her husband. She picks up a note that was slowly pushed under the locked door.
She reads it aloud, "Helene, I've had some trouble. I've had a serious accident. But I'm not in danger at the moment, although it's a matter of life or death. It's no good calling to me or saying anything. I can't answer. I can't speak." He asks for a bowl of milk laced with rum. She prepares the concoction and returns to the lab, knocking three times to gain entry. Andre lets her in.
A note explains that he needs her to find a fly with a white head. She remembers Philippe's find from earlier that day. Andre has a black cloth covering his head and keeps his left arm hidden in his lab coat pocket. He slurps up his milk while Helene searches for a fly she knows is not there. She recounts the story her son told her. Andre gets up and his fly arm is revealed. Helene screams.
Andre motions her out of the lab, then locks her out. He types the next set of instructions for his wife. The next morning Helene wakes. She thinks the whole episode was just a nightmare, but her morning meeting and typed note confirms the nightmare is real. Andre explains that his experiment by transmitting himself the first time was successful. A second try was not so.
The note explains, "But in the second experiment, a fly which I did not notice was in the disintegrator with me. When we integrated again, our atoms were mixed. Now my only hope is to find the fly. I've got to go through the machine once more and pray our atoms untangle. If you can't find it, I'll have to destroy myself." Helene asks to see her husband's face, but he refuses.
Helene tells Emma that they must find a fly. She presses her son into service to find the special fly. Helene screeches at Emma, who misunderstood the request and killed a fly with a swatter, "I said catch them! Dont kill them!" After Philippe returns with no luck, he and his mother spot the fly on a lamp shade. The head and one leg are indeed white. They carefully approach it, but it flies over to the window.
Helene puts out some sugar to attract their prey. Philippe catches it, but it escapes the net. It escapes outside through a broken section of the glass. It is now outside and Helene and Philippe search for it. Helene is exhausted and exasperated. She returns to the lab and tells her husband of their bad luck.
While he attempts to eat, she reads his next note, "If you had caught the fly, you would not be reading this. I know you will never catch it now. It's hopeless. There are things man should never experiment with. Now I must destroy everything, all evidence, even myself. No one must ever know what I discovered. It's too dangerous. I've thought of a way. It's not easy, but I need your help."
She pleads with her husband not to destroy himself. She convinces him to transmit himself one more time, even without the fly. Transmission is successful, but without the fly, he is the same. She pulls the black cloth away, then shrieks with horror at the visage. Andre has the head of a fly.
We see Helene as Andre now sees her through compound eyes. She backs away from Andre and faints. He picks her up and places her on the couch in the lab. He comforts her with his good arm and hand, but can't control his fly arm that means to harm his wife. He goes on a rampage and destroys the delicate electronic equipment.
He burns all his notes. Helene wakes and approaches her husband. She recoils from Andre as he approaches her. He retrieves the black cloth and puts it back over his head. He erases the blackboard, then scribbles another note to Helene, "No use now--help me--but don't come near me. Kill fly, please. Love you."
She follows him to the factory next door. He starts the press and points to the red button. He places his head and arm under the press then motions for her to start the press. The press crushes Andres fly head, but his arm is still untouched. She resets the press, places his fly arm on the bed, then directs the press down a second time. The story is finished, and we are back in the present.
Charas is told Andre destroyed his notes, but she erased his note on the blackboard. Charas thanks her for telling the story. Francois and Charas prepare to leave the house. Charas promises, "I'll be back at 10:00 with a warrant for her arrest on the charge of murder. Nurse Andersone is under strict instructions not to leave her for any reason. I'm satisfied now. She's quite insane. She won't hang."
Charas provides a glimmer of hope to Francois, "Show me the fly." The next day Francois returns to the house and asks Emma about the fly. She tells Francois it was just a fly. Francois sits on a bench in the garden, oblivious to the fly caught in a spider's web. It cries out for help, but Francois cannot hear it. It is now 10:00 a.m. and Charas has returned, as promised, with his warrant and an ambulance to transport Helene.
When told of her arrest, Helene reacts by asking Francois to show the inspector the fly. Francois admits he never had the fly. Francois takes Philippe outside so he can't witness his mother's arrest. He mentions he saw the fly again, "It's in a web. A spiders going to get it. By the bench in the garden." Francois retrieves Charas. They walk out into the garden.
Charas and Francois see the tiny arm and head on a fly's body and the spider ready to pounce. The tiny thing screams, "Help Me!" As the spider covers its tiny victim, Charas picks up a rock and crushes both. Francois accuses Charas that if Helene killed a man with a fly's head, then he is as guilty for killing a fly with a man's head. They collectively concoct and agree to a scenario for suicide.
Sometime later, Philippe and Helene are playing croquet in the yard. Francois arrives to take his nephew to the zoo. In reply to his nephew's query about his father's death, Francois tells Philippe, "He was searching for the truth. But for one instant, he was careless. The search for the truth is the most important work in the whole world and the most dangerous." We close with Helene escorting her son and Francois out of the yard.