Klaus Kinski is John Alexander who is initially seen in Riccardo Freda's A doppia faccia (Liz and Helen) (1969) as a meek, quiet and ineffectual husband to Helen (Margaret Lee). The two met while skiing in Switzerland and immediately fell in love. Upon return to London, the two married, and John took a position in Helen's business organization that her father controls as chief executive officer while Helen holds the majority ownership interest. Okey-doke and goodbye love. John and Helen's home life is riddled in strife: Kinski's John broods in the hallways, parlors, and foyers, wondering why his wife is so cold to him; and cool Helen has no time for John as she spends more time with equally cool and equally beautiful, Liz (Annabella Incontrera). Helen decides to take a solo trip in her Jaguar, and her car crashes, causing her death. Scotland Yard determines Helen's death an accident yet when John takes a three-week vacation in St. Tropez, following his father-in-law's suggestion, the police become suspicious and open an investigation. John comes home to a dark house and finds a beautiful blonde showering. Her name is Christine (Christiane Kruger) who didn't think John would mind.
Huh? What? Christine parades around the boudoir nude and asks for a drink and a cigarette to a perturbed John. Christine is successful in only securing a ride from him. He takes her to Soho where she flees from the car with his car keys in hand. John finds her in a flat where a private film screening is taking place. The film appears to be a loop where Christine walks into frame nude in front of a veiled woman on a four-post bed. Very provocative. The veiled woman has a scar on her neck and is wearing an unusual ring. John recognizes this jewelry and the woman's scar as belonging to his dead wife, Helen. Did Helen have a shady cinematic past or is this the new Helen, not really dead. John broods to begin his investigation.
At this point, like Lucio Fulci with Una sull'altra of the same year (Fulci shares a story credit on Liz and Helen incidentally), Riccardo Freda can take his story in three directions: a deductive murder mystery with John as prime suspect; an amateur giallo-esque mystery with John as sleuth with the mysterious veiled woman as the object of his investigation; or John can plumb the provocative depths, tumbling further into the looking-glass, opened by sultry sprite, Christine. Freda chooses all three, creating an uneven and unsuccessful film with A doppia faccia. 
To begin with, as a deductive mystery, A doppia faccia clearly fails. The only expository clue left by Freda is an insert shot of a black-gloved hand tampering with the brakes on Helen's Jaguar. Beyond the obvious fact that Helen's crash was intentional, little is shown to the viewer to begin an investigation. As to whom has the strongest motive for murder, none of the first-act's participants, John, Liz, or Helen's father, have one. Therefore, Freda and Scotland Yard have to manufacture one. With nothing at the crash scene in the way of direct evidence to implicate a suspect, the police focus on a wisp of circumstantial evidence: John's three-week vacation in St. Tropez. Other circumstantial evidence is presented in Liz and Helen, yet what the police choose to focus upon is far from the obvious. Since Freda only conveniently drops clues for his viewer, the viewer is playing catch-up with the mystery, and virtually no suspense plays out from this thread of the film.
Kinski's John is immediately taken with discovering the identity of the veiled woman in the film. As to why is unknown. This aspect of the story becomes Freda's strongest. For example, Kinski's John is shown as quiet, brooding, and ineffectual at the beginning towards Helen; yet when Christine enters his life, Kinski violently changes his personality. He has no problem getting physical with Christine: he grabs her and shakes her; yells at her; and even beats her in order to gain information about the veiled woman's identity. This juxtaposition of John's character makes the viewer wonder as to if this is the real John, and Freda was cleverly masking this aspect of his personality during the first act. The link is both characters of Helen and Christine: each is, in a very traditional, superficial, and stereotypical sense, a deviant in society and from a traditional moral perspective. Although Freda is never overt, there is the overwhelming sense from the first act that Helen's lack of affection towards John and her strong kinship with Liz are more than they seem. Helen's real affection and love are for Liz; and her marriage was a sham for polite society with John as a victim of unrequited love. Kinski's signature brooding with his performance as John hid a simmering anger towards Helen (and possibly women). When he meets Christine, who is engaged in both prostitution and pornography, his anger towards Helen comes to the surface, and John acts out towards Christine as he wished he would have towards Helen. Or, perhaps within the shadows of the domestic scenes of the first act, Kinski's John was violent towards Helen (where she got that scar on her neck is wholly unknown). Unintentionally- or intentionally-crafted, these scenes from Freda are his strongest and most engaging. The two traditional "deviants" are seen in a different perspective while Kinski's character becomes, at times quite effectively, more sinister. These themes are signature giallo, especially the misogynistic aspect; yet Freda moves little beyond themes within A doppia faccia, as Kinski's John does little in the way of investigation. Like the viewer, John stumbles through his investigation with whatever Freda gives him, instead of picking up clues and deducing what to do next.
Finally, Freda can just let go in A doppia faccia (as the Italian title suggests) with his main character, John (and all of his other characters, for that matter). Liz and Helen is shot cleanly and focused with totally uninteresting shot designs. This mechanical conservatism with Freda's compositions carries over into the substance of A doppia faccia. Virtually no eroticism is present throughout, despite the fact that Freda and company want to be provocative with the Soho subculture and Helen, Liz, and Christine's characters. The depiction of Helen's character is just cold. Some insight into her character with dialogue or a confrontational scene (really anything) would have been welcomed. Arguably Incontrera's Liz is not a character at all: Freda gives the viewer almost nothing behind Liz. She is a plot device for a later revelation and becomes a potentially provocative character wasted. Kruger's Christine gives A doppia faccia a lot of energy, but Freda uses her also as mostly a plot device. The brilliant set-ups, of which there are very few, like Helen and Liz alone or Christine's first fortuitous meeting with John are undercut and poorly handled. Overall, too much thought went into mechanics in making A doppia faccia, and too little thought went into creating emotion, energy, or artistic flare. The set design, however, is beautiful, and Kinski gives another excellent, yet perfunctory, performance.The fact within the first sentence of the third paragraph about Fulci's contribution to A doppia faccia is from Beyond Terror: The Films of Lucio Fulci by Stephen Thrower, FAB Press, Surrey, England, U.K., 1999.
Kinski, like the actresses, was chosen by Di Leo's for his "dramatic face," and like the ladies, he's eye candy. Klaus Kinski plays Dr. Francis Clay who has a burgeoning love for Margaret Lee's Cheryl. Kinski's expressionistic face with his piercing eyes and brooding demeanor hides mystery (which Di Leo plays on). Kinski walks the halls and gives some of the most uncomfortable cigarette-smoking sequences (I'm not a gambler but I would bet Kinski is not a smoker). Kinski and Lee display a light romance, straight out of any dime-store paperback.
To Di Leo's credit, the compositions of the killer are well shot. In a haunting sequence, the killer is brandishing a sword, and all alone he swings it in a madman's fury before his next frenzied kill (the swings of the sword are accompanied by low-octave notes delivered by Spadaccino's minimal score). In a humorous (yet effective) scene, a nurse passing the grounds at night walks within inches of the killer and does not notice him. A scythe is in the bushes, and as soon as she passes, the killer picks up the scythe to decapitate her. The nurse turns and screams before her death. The scene comes off as the very definition of perfunctory: okay, I'll walk by you and pretend you're not there. Get the nearby weapon, which I also conveniently fail to notice, and kill me.