Frank (John Pollono), Swaino (Jon Bernthal) and Packie (Shea Whigham) are the kind of best friends that strangers would assume are family. The Boston Red Sox fanatics finish each other’s sentences while roasting one another all inside five minutes, something that doesn’t build grudges or present smooth evenings. Souls united by experiences and acceptance instead of blood, the three men are prone to fist fights and a war of words, but they will also lie down in the street for one another the next day.

The one thing that unites the three, even through the harshest of times, is Frank’s daughter, Crystal (Ciara Bravo). The fiery yet smart young woman acts like a magnet for the three misfits, pulling them back together for one crazy night at a car repair shop. Saying more would only spoil the goods, because part of the charm of “Small Engine Repair,” written and directed by Pollono, is its unpredictable nature. You never know where it’s going, but the characters and environment keep you invested throughout the 103-minute running time.

No, there isn’t a huge reveal at the end that upends the film, like Packie quietly working for the Feds or Frank actually being a low-level gangster. The surprises here revolve more around human nature, unexpected humor and dedicated performances from the cast. Pollono isn’t an actor name that pops right into your head, but he’s the glue here in a performance that stands on a wicked combination of comfort and edge. He is mostly known for writing the powerful Jake Gyllenhaal Boston bombing drama, “Stronger,” but he puts in fine work here as the patriarch of the group, aka level-headed thinker. Frank isn’t without his own temper explosions but if there’s reason to be found in a bar fight, it starts and ends with him.

Bernthal’s Terrance, aka Swaino, is the ladies’ man with the polished looks, nice clothes and energetic swagger of a guy who walks into a room where his ego already set up shop five minutes earlier. And the actor leans into that persona, igniting his effortless charisma and blunt physicality.

Whigham’s Packie is a literal trip. A constantly moving storm of nerves and dirty humor, he has the 24/7 neurotic nature of someone whose mind can’t slow down, even if he is arguably the smartest and most perceptive of the group. Whigham visibly lost weight for the role and turned in one of his best performances. Every do-or-die group of friends needs a Packie.

The lived-in aesthetic of the film lends itself well to the acting, which isn’t forced–not even the Boston accents. The majority of the fast-moving film is spent with the three best friends and their shenanigans, whether that be a bonfire outside Frank’s house or a family meeting involving Crystal. She keeps the boys in line, even if their age dwarfs her own. Bravo is a gifted actress who knows how to make her screen time count.

Pollono’s script does have a few tricks up its sleeve though, and non-linear storytelling is one of them. All the answers don’t exactly pour into the film via exposition or a quick flashback. Some of the key plot developments are called back upon later when the timing is right.  Audiences will be guessing what the exact predicament is with Crystal, which brings the three men back together for an unforgettable night, without knowing what is happening. By the time Frank’s ex (the wonderful Jordana Spiro) and up-to-no-good Chad (Spencer House, used well here) show up to the car shop, things start to get very interesting… and a little bloody.

Nothing is forced in “Small Engine Repair,” and that’s a golden element for me. Some may not like the unknown plot threads being tied off late approach, but it worked for me. The older the movie gets, the more you know and that puts the viewer into the same seat as most of the characters. For a movie and script based and adapted from a play, you don’t get too much of that stage-reading atmosphere either. Dialogue driven but unconventional, Pollono’s film entertains in unique ways.

This is the kind of movie where one older guy shows another older guy how to effectively use Instagram in the middle of a chaotic moment, and it’s not awkward at all. The social media platform is used wisely here, both in the machinations of the plot and as a constant comedy tool. Old lion-headed adults fidgeting around with IG gives a film with a darker edge to it some much-needed lightness. If a drama can produce laughs without losing focus, there’s something worthwhile going on.

The cast is the heart and soul, though. Pollono, Bernthal, Whigham, Bravo, Spiro and House are all terrific in their own ways. If someone steals the film, it’s Whigham. I could go on and on about his performance. He’s been in countless films in the past 10 years, but none of those creations had as many layers and surprises as his Packie. He’s the best friend every signature group needs, the loose cannon with a brain and fearlessness. The actor gives it his all in a role that shouldn’t be forgotten about come awards time.

“Small Engine Repair” is funny, will keep you off balance with its plot without alienating your brain, and has a decent heart that doesn’t get too dark. If you like unexpected family dramas that feel different, this one’s for you. I’ll be watching it again.

It arrives this Friday in select St. Louis cinemas. Also, keep a lookout this Friday right here for an exclusive interview with Bernthal, Pollono and Whigham on making the film and becoming real-life best friends in the process.