One of Brendan Gleeson’s best lines, from any of his films, is in Neil Jordan’s The Butcher Boy (1997) — an adaptation of Patrick McCabe’s heart-breaking book. Little Francie Brady (Eamonn Owens), the film’s unstable protagonist, sits in the office of Father Bubbles (Gleeson) and helps himself to some biscuits. The priest then tries to coax the boy into keeping quiet about having been molested by Father Sullivan (Milo O’Shea). In this particular scene, Gleeson is at once desperate, charming and deranged, raising a cheek up to crack open one side of his mouth into a madman’s smile.

There is no analytical framework to guide audiences towards a hollow understanding of raw talent. Gleeson’s charisma is built-in, like all legendary performers, and this is most evident when his characters behave despicably. The Guard (2011), written and directed by fellow countryman John Michael McDonagh, tells a story about one man’s colossal intelligence and humor, which he uses at other people’s expense. As a collaboration between McDonagh and Gleeson, Sergeant Gerry Boyle is an intentionally belligerent policeman in County Galway, a rural area in West Ireland. Boyle seems like a big kid in a small playground, but many of his colleagues hate him or disregard him as a fool.

Gleeson has made two films with McDonagh, of which The Guard contains the greatest sum of the actor’s pin-sharp and irresistible line-delivery style. He was not only given the screen time he deserves but the dialogue to match his presence, as the director writes comedy and melancholy into single sentences, much like his filmmaker brother Martin McDonagh (In Bruges, Three Billboards Outside Ebbing, Missouri). In The Guard, Gleeson sets the rhythm with his performance and rides the melodies of his character’s complicated mood swings. He can be kind when being rude, angry when dull, or feel love in its classic form. He’s a chameleon, as Gerry Boyle is drawn in and out of his many exteriors. In a single scene, Gleeson plays the fool, the out of touch middle-aged man, the hero and the joker. From the character’s dead-eyed ignorance, his face can drop into a smile as sudden as a coin rolling off a table. With the same quickness, Gerry’s body twitches with grief.

There’s a running joke in The Guard where the locals scoff at the idea that drug-related crime is anything worth bothering about. Galway is a prime location for cross-Atlantic drug trafficking, and Don Cheadle’s FBI agent, Wendell Everett, has been sent over from “the States” to help the Gardaí catch a group of criminals. Few understand Sergeant Gerry Boyle, but his central friendship with Wendell develops only because Cheadle’s character can see through Boyle’s façade, including the insults he hurls at people, many of which are directed at the FBI agent. Just on the cusp of this realization, Wendell admits that Gerry has him confused: “I can’t tell if you’re really motherfucking dumb, or really motherfucking smart.”

Gerry’s relationships expose his good nature, and while his friendship with Wendell is The Guard’s most entertaining, there are touching moments with Boyle’s dying mother, the widow of the sergeant’s new partner and a young boy. A combination of McDonagh’s sharp dialogue and Gleeson’s performance present Gerry as a man whose true character appears in fragments. Boyle befriends his deceased partner’s widow, Gabriela McBride (Katarina Cas), a Croatian immigrant who married for a green card. There is a subtle romance between Gerry and the woman, and in turn the sergeant is revealed to be a lonely man. Near the end of The Guard, the sincerity of Boyle’s affection for Gabriela is folded up like a secret note with the last thing he might ever say to her: “I just wanted to say I’m sorry I didn’t get to know you better. You’re a lovely woman.”

Gleeson ensures there is no doubt when Boyle is being sincere or when he is trying to wind people up, a line the actor has to cross frequently as expected by the script, but which he does with fluid changes in his tone and body language. Contrast the scene where Gerry sneaks his mother out of the hospice and a previous moment where Boyle chastises an IRA man with Four Lions-levels of ridiculousness. After Pat Shortt’s Colum Hennessey questions Boyle about some missing guns, which the sergeant was returning as a “favor,” Gleeson’s character says, “You have your explosives, don’t you? It’s not as if you lads were ever that keen about getting in close for scrap.” But Boyle’s sharp tongue is numbed when sitting in a bar with his mum. With the tiniest jolt of Gleeson’s head, Gerry suddenly resembles a child as his mother strokes his face, perhaps the only time in The Guard when Boyle is not completely in command of himself.

There’s an odd sort of symmetry to Boyle as a character and Gleeson as a performer. The sergeant’s unpredictability is essential to how he disarms people, while the actor makes sure that Gerry’s real intentions are always there for the viewers who are willing to participate. Cynicism runs rife in this little town. The traffickers pay off the Gardaí easier than Wendell is able to gather information from the locals. Boyle chooses to opt-out of the collective indifference — he is willing to do his job because of a moral imperative. Even Boyle’s refusal to take money from Liam Cunningham’s Francis Sheehy-Skeffington earns his and the other traffickers’ respect. “It’s not often you come across that kind of integrity in our business.” Boyle is too sympathetic to be an anti-hero, though anyone brave enough to call him a hero to his face would likely be ridiculed. In Boyle’s own words, he is “the last of the independents.”

The Guard not only takes the western to the west of Ireland, but also the quick-lipped and cutting wit of early American screwball comedies. McDonagh has named Preston Sturges, Sam Peckinpah and John Ford as influences on his work. With cinematographer Larry Smith’s own vision of troubled leading men navigating paths of striking color and light, McDonagh created a colour scheme that recreates Boyle’s sense of the world, one ripe for mischief. The original music by Calexico is a similarly riotous and movie-referencing joy, taking McDonagh’s influences literally. Battered guitar strings and belting horns could be the only complement to Gleeson sitting in his underwear after dropping acid, stolen from the dead bodies of a car crash, in the middle of the day.

McDonagh has said that with Calvary (2014), he was challenging himself to write the story of a “good priest.” The man of God in Robert Bresson’s Diary of a Country Priest (1951) is a tempting comparison (one the director has made himself), in particular the way the priest tries to mediate the disputes between his parishioners and interpret the dwindling respect they have for him. In Calvary, Gleeson’s Father James Lavelle tries to maintain his faith in a time when his church is no longer trusted, and for reasons he accepts. Both Lavelle and The Guard’s Sergeant Gerry Boyle crash into scenes because Gleeson’s physicality demands attention, even in the way he turns his head. In addition, the integrity that he soaks into his characters is typical of a performer whose work is always personal. Only Gleeson could’ve pieced these characters together from McDonagh’s page and completed them in his own image; characters who are at once hated and admired, feared and mocked, by the same people they are trying to save.

Mark Seneviratne (@sene_mark) is a data analyst and writer based in Manchester, UK. He has published a short story in Not One of Us and numerous essays on film for Vague Visages, Film Inquiry and The State of the Arts.