Richard Fleischer's 1968 film The Boston Strangler, based on the true life series of murders that took place in the Boston area in the early 1960s, is a powerful (and early) cinematic depiction of the activities of a serial killer (a phenomenon which has come to dominate much TV and film drama in recent years).
In fact, the film is, certainly during the first 40 minutes or so, actually quite a pedestrian affair, albeit the use of split screen cinematography during the (off-screen) murder scenes lends an effective, near-documentary feel to the film. The early sequences contain rather too many wooden and clichéd performances (and dialogue) to be convincing, and the frequent shots of media coverage of the grisly events have been conveyed more effectively in other, similar, films - examples that spring to mind include Richard Brooks' In Cold Blood and the more recent Zodiac. It is also interesting (and alarming) to see how the film portrays its, now very dated, views on homosexuality, as a rich, gay man is apprehended on suspicion of being linked to the murders.
It is not until, first Henry Fonda, playing the police officer (John Bottomly) tasked with co-ordinating the investigation, and then, second Tony Curtis, as Albert DeSalvo, the actual perpetrator of the crimes, are introduced onto the screen that the film really begins to become more compelling. Indeed, even Curtis is relatively deadpan (or even wooden) in his early scenes, and it is not until the latter interrogation scenes that both Curtis and Fonda begin to deliver two top-rate performances. In these scenes, as it becomes apparent that Curtis is suffering from schizophrenia (a fact emphasised brilliantly by showing Curtis and Fonda frequently alongside a full length mirror), his performance becomes more and more intense as this realisation dawns on him. By the film's close, Curtis has delivered, for me, a performance (albeit of a very different nature) to rank alongside his two other outstanding film performances, in The Sweet Smell Of Success and Some Like It Hot. The film's final shot, as the camera pulls back from DeSalvo in his interrogation cell is also brilliant, and reminiscent of the closing shot from Hitchcock's Psycho.
In summary, a film which improves as it progresses, lifting it from three to four star territory.