The story begins in the West Germany, where Hans Weimer (Tristan Roger, later to appear in producer-director Pete Walker's The Flesh and Blood Show and another softcore sex film, the Spinal Tap-esque titled Sex Farm) is recruited to travel to London to investigate what has happened to au pair Greta (Leena Skoog).
Hans first makes contact with Mrs Marks, with whom Greta was originally living. He learns that Greta was unhappy with the poor treatment she had received at the hands of the Marks family, who regard au pairs as “a type of servant” and whom Greta left after only a week. Hans in turn considers Mrs Marks as a “sow”, a term that gains additional resonance given Hans's nationality and the implication of the Marks/Marx name and Golder's Green residence, in that she is coded as Jewish.
Hans then meets up with Sue, with whom he visits clubs and discotheques, and makes contact with another of Greta's acquiantances, Serena; Walker, making a Hitchcockian cameo as a waiter, gets a pie in the face.
Serena tells Hans that Greta was a nasty piece of work, who exploited her and her friend Kristina, before then leaving them to work at a Soho strip club with Cynthia. (The man enticing men into the club has a patter that likely intentionally references Paul Raymond's approach, of having nude models who move rather than stay static, this prompting a raid from the clearly corrupt police.)
Hans then learns about footballer Roger Maitland (Robin Askwith), who takes a more active role in determining what has happened to Greta...
This confusingly titled entry might be considered the Citizen Kane of the British sexploitation film. That's not referring to its quality, which is no better or worse than most comparable films within the genre and time period, as much as its structure. For it is one that sees the investigator protagonist visit a series of characters who reveal what they know about the missing Greta, A mentioning B, then B mentioning C etc. These flashbacks scenes are presented in black and white, green and red, and in 3D rather than in colour and 2D, with this coding being identified in the opening credits rather than being left for the spectator to figure out. The flashbacks also feature a lot of crude “comin' at ya” shots of things being thrust forward from the screen.
One important area where The Four Dimensions of Greta -- in 3D departs from Welles's film is in placing the diegetic investigator and the viewer on an equal footing. In Welles's film the investigator never learns what Kane's dying utterance, “Rosebud”, refers to. Here, by contrast, we and the investigator simultaneously learn what has happened to Greta.
Another area where the film's classical aspect is evident is how these flashbacks are discreet and largely non-contradictory. This contrasts with another key film exploring the flashback and its relation to truth, Rashomon. Akira Kurosawa's film presents the same incident from a variety of self-interested and subjective perspectives, none of which -- including the observer who was not a participant -- can be trusted to convey the truth.