“He was everything larger than life that I had expected him to be (sic)," the actor Randeep Hooda said in an interview to a daily paper, “He was so full of life, almost virile. He is such a handsome man. Even at age 72, his aura is fully intact."

By the time this gush-fest ends, the reader may have lost sight of the fact that the big incandescent blob of charisma being talked about—and the man Hooda plays in the new film Main aur Charles—is the serial killer Charles Sobhraj, who has spent over 30 years in jail (in separate stints) for his crimes.

But no, I’m being unfair to Hooda. An actor doesn’t have the luxury of being judgmental: he has to try and understand—even, to whatever degree possible, empathise with—the character he is playing. And Hooda is very good in Main aur Charles. The true scope of his performance and presence is felt gradually, as the film itself—directed with flair by Prawaal Raman, and wonderfully shot, often in dark shadowy settings, by Anuj Rakesh Dhawan—goes from being a disjointed (and puzzling) collection of vignettes to one where the narrative comes together more fully.

The real-life Sobhraj was a charmer, and this was integral to his success at doing the things he did; it’s unreasonable to expect a film to present him as unattractive just to make a moral point. (Whether it should go as far as putting the tagline “Worth Dying For" on the poster is another debate!) Speaking more generally though, film history is dotted with magnetic villains, and with the accompanying question: is it okay to make evil seem seductive?

The answer appears clearer in some cases than in others. When Adolf Hitler is depicted in godlike terms, descending from the clouds in a plane to greet the people and lead Germany to glory, in the 1935 documentary Triumph of the Will, it is relatively easy to say (with hindsight) that Leni Riefenstahl’s film was irresponsible, or even wicked.

We wince at those images and turn for succor to scenes that threw a banana peel under the thick boots of fascism, such as the opening of To Be or Not to Be (1942), with Hitler (this is an actor playing Hitler, but we don’t know that yet) apparently window-shopping at a Warsaw market, and being gawked at and gossiped about.

At other times, even when a bad-guy film has its heart in the right place, the casting may introduce a dimension that was not intended. In 1968, Tony Curtis played the notorious killer Albert DeSalvo in The Boston Strangler (a film that has minor structural similarities with Main aur Charles). He was deglamorized for the part, and it was a daring performance, but that didn’t completely take away from the fact that here was a Hollywood golden boy, a matinee idol who used to be associated with swashbucklers and romances. To a Curtis fan, might DeSalvo become easy to relate to on some level?

The dashing, blank-slate villain has quite a fan-following too. Anyone who has read Patricia Highsmith’s Tom Ripley novels will see that Sobhraj—at least as depicted in Main aur Charles—is a cousin to Highsmith’s amoral anti-hero, who slips from one personality to another as he prepares his crimes. Unsurprisingly, Ripley has had some gripping cinematic avatars, from Alain Delon in the 1960 Plein Soleil to Dennis Hopper in The American Friend and Matt Damon in The Talented Mr Ripley. In fact, thinking about Charles and Ripley, I realised that the “Main" (me) in the simple-seeming title Main aur Charles doesn’t have to be police commissioner Amod Kanth (Adil Hussain), who is Charles’s nemesis and the story’s po-faced moral centre; the “me" could just as easily be a second, hidden Charles. At one point he is shown fake passports bearing his photographs and assumed names, and asked: which of these people are you? “All of them," he replies tersely. But is there a real person beneath the disguises, or only one final blank mask?

Which brings us to the film’s doppelganger theme with its view of good and evil as inextricable sides of the same coin. In popular culture, the idea has been iconized in some of the darker comics about the Batman-Joker relationship (see Alan Moore’s brilliant Batman: The Killing Joke, with its closing yarn about two lunatics trying to escape an asylum together) and you’ll also find it in the relationship between gentleman cannibal Hannibal Lecter and his pursuer Will Graham. “The reason you caught me is that we are just alike," says Lecter to the spooked Will in the 1986 film Manhunter, a theme that has been more fully developed in the ongoing TV series Hannibal.

In fact, the title of Raman’s film reminded me of the two Charlies in one of the best doppelganger movies I have seen, Alfred Hitchcock’s 1943 Shadow of a Doubt: in one corner is the lady-killer (in both senses of the term) Uncle Charlie, in the other is his adoring small-town niece, who was named after him. Often linked together visually by the film, they have a near-telepathic connection—the difference being that the younger Charlie is uncorrupted, while the older one is a murderer and a nihilist. In the end he is tossed off a train; good triumphs over evil. But it isn’t that simple either. We are left with a clear sense that the once-innocent world of the younger Charlie has been forever altered. It’s a bit like the spooky scene in Main aur Charles where Amod Kanth’s wife, having become intrigued by the Charles story, tells her husband, “He was involved with dozens of women, and you can’t even handle me alone?" and the otherwise straight-arrow cop looks at her and bursts into a convulsion of laughter, his eyes gleaming like those of the man he is pursuing to the ends of the earth.

Above the Line is a fortnightly column about Hindi cinema and how it presents the world. Jai Arjun Singh tweets at @jaiarjun.