University lecturer Adam Bell (Jake Gyllenhaal) teaches a history course where he goes over the dictatorships that have existed since time immemorial, and part of the observations he likes to make on them is that history repeats itself, as these arrangements never happen just the once, even if the construction and method of the totalitarian states have different ways of sustaining themselves. When he's not intellectualising, there's not much more to his life: he buries his face in a book, rarely socialises, and mainly uses his live-in girlfriend Mary (Mélanie Laurent) for straightforward sex, not exactly catering to either her emotional needs or his own, but they are set in their ways now. That is until a colleague suggests Adam wind down with a movie...
Imagine if the fellow tutor had recommended Enemy rather than that, though Adam would have been no less disquieted by what he watched on the screen: his own face looking back at him. In the case of the film he rents, it's a light comedy but he doesn't find it funny when he spots a supporting player in the tiny role of a bellboy who is the spit and image of him, and immediately his life is on a course to turmoil. It's as if by jumping the rails of his routines by acting slightly out of character he has discovered a whole new side of himself he never knew, indeed, it's more than a side, it's a whole new person. So what does he do? Say "Fancy that!" and go back to those routines, or try something more against his better nature?
It wouldn't be much of a movie if Adam took his doppelganger in his stride, and the title appeared to be alluding to the phrase of someone being their own worst enemy, as the book this was based on was called The Double, a work by Nobel Prizewinner José Saramango which director Denis Villeneuve and screenwriter Javier Gullón took as a jumping off point into a deliberate melange of audience baffling weirdness, often featuring a spider motif that was not present in the original. The arachnophobes were advised to stay away, since the imagery that intrudes may be from Adam's nightmares - a mysterious stage show that opens the movie has a large tarantula as its star attraction, for example - was eerily accurate to the sort of thing that showed up in the harder to shift night terrors they might endure.
On paper, Enemy had a plot that made a kind of sense in a loose manner, as it was about a staid academic finding a world he was astonished by, and one which threatened him in a fashion he could just about grasp, as if this was influenced by the short horror stories of M.R. James, that sense of a personal quest leading to equally personal dismay shared by many of the English author's classic tales. In this case, it was Adam's need to track down his double, who turns out to be a largely unsuccessful actor named Anthony Claire who is on the brink of fatherhood with his very pregnant wife Helen (Sarah Gadon), one of a trio of strong women in the plot. In contrast to the rather cold Mary, lookalike Helen is emotional and nurturing, which is also a contrast to Adam's actual mother (Isabella Rossellini) who may have something to hide, such as being Anthony's mother.
Not that we are told with any clarity, but then there's a lot left unexplained by the end of the film, not least what that final scene was about, one of those European arthouse finales which raised all sorts of questions and deliberately left the audience discomfited, even disturbed thanks to a striking image and utter lack of anything to hold on to as far as sense and reason went. Although Villeneuve and Gyllenhaal worked together again on Prisoners, that later effort was released first, which was fairly savvy since that was more conventional than anything here, actually there was no guarantee there would be a substantial crossover between fans of either. Whatever, they were certainly beneficial for one another as director and actor, especially in this case where they took themselves to bizarre places, moving towards horror movie territory but too invested in their adulterous relationship drama the scary bits commented on to really be termed an all-out fright flick. If Adam and Anthony were the same person divided by choices either could have made, that would explain a lot - and little.