Nightmare

• Shot at Hammer's own Bray Studios and nearby Oakley Court in Berkshire from December 1962 to January 1963 — not a rented soundstage, which kept the modestly budgeted psychological thriller in Hammer's home territory.
• Freddie Francis, primarily a celebrated cinematographer, directed only a handful of features; this was his second film for Hammer, following Paranoiac (1963) and shot before he moved on to The Evil of Frankenstein later that same year.
• In the UK the film was shot and initially billed under the working title Here's the Knife, Dear: Now Use It (also later distributed as Satan with Long Lashes); Universal released it in the U.S. on June 19, 1964, under the simpler title Nightmare, double-billed with The Evil of Frankenstein.
• Jimmy Sangster's screenplay pulls off a rare double twist: the audience thinks the mystery is solved once Janet stabs a woman she believes is her ghostly tormentor, only for a second act to reveal her nurse Grace (Moira Redmond) staged the haunting with guardian Henry Baxter — a scheme that then collapses in on the schemers themselves.
• Moira Redmond plays Grace Maddox, the nurse-companion whose disguise as a scarred 'woman in white' drives the story's central deception; Janet's actual institutionalized mother is played by a different actress, Isla Cameron, in the asylum-set prologue.
• The BBFC classified the film (with some cuts required) in October 1963 for its X-certificate cinema release, restricting it to audiences 16 and over under the classification system of the day — standard for a Hammer thriller built around stabbings and staged insanity.

The film operates as a metatextual trap on the audience itself: for much of its runtime we occupy Janet's POV, accepting her terror as authentic madness, only to discover we've been gaslit alongside her. Sangster's structure argues that horror cinema is inherently a confidence game — and the real monster is whoever controls the narrative frame.

Janet's mother isn't just backstory; she's the film's buried thesis about inherited female trauma. Every woman in Janet's orbit — the teacher, the housekeeper, the disguised nurse — becomes a mother surrogate, and the conspiracy reads as an adult network deciding a young woman's fate through institutional power rather than supernatural forces.

The nightmare sequences may not be dreams at all but Janet's suppressed accurate perception — she's actually sensing the conspirators staging events, and her 'madness' is her mind trying to reconcile what she witnesses with what she's told. The film's rewatch supports this: Janet is never wrong about what she sees, only about what it means.

Janet is a boarding school student tormented by nightmares about her mother, who went mad and stabbed her father years ago. Her dreams bleed into waking life when she spots a scarred woman lurking in the shadows. Shipped off to a country house under a sympathetic teacher's care, Janet spirals further, convinced the woman is stalking her. The house staff watches with unreadable faces. A knife appears. Janet's grip on reality frays until she plunges a blade into someone — and the film's carefully stacked deck collapses, revealing who's been engineering her breakdown and why.