The pleasures of “Gringo” are the pleasures of genre: It’s a fun type of movie, but it’s not a good version of the type. The movie throws together various shady and colorful characters and has them cross paths and create trouble. The movie is heavy on coincidences, heavy on the wrong person always showing up at the right time, and it goes for a certain mood — a zaniness that doesn’t preclude the likelihood that lots of people will end up dead.

Setting up a movie like this is easy. What’s hard is bringing it all home. And so, not surprisingly, the beginning is strong, and then it goes downhill as the audience starts getting that Peggy Lee feeling (“Is that all there is?”). “Gringo” is a puzzle with too many pieces, or not enough pieces, or maybe it’s a bunch of pieces from several different puzzles. But one thing is certain: It’s never going to fit together.

It’s the first feature from director Nash Edgerton, whose brother Joel Edgerton plays a pharmaceutical executive who gets involved with Mexican drug dealers. He’s having an affair with two women, a cold-blooded fellow executive (Charlize Theron) and the wife (Thandie Newton) of his supposed friend and underling, Harold (David Oyelowo). Harold is the title character, known as the Gringo in Mexico, even though he is an immigrant from Nigeria.

Though the script is too scattered to follow any character, Harold is the main focus, the one truly innocent and decent fellow in the story. It’s a convention in this kind of story to take the lead character from innocence to wisdom, and “Gringo” tries to copy that pattern, but it fails to do so in a satisfying way. Basically, a plot like this either works like a Swiss watch or it’s a stopped clock with the springs sticking out. There’s no in between. By that measure, “Gringo” is a stopped clock.

But it’s not without its pleasures. Because it’s not excessively (or even appropriately) weighted down by sense or logic, the movie’s characters can be extreme, and extreme characters make for good scenes. Carlos Corona makes a couple of memorable appearances as a vicious yet amusing cartel boss. Theron has fun glorying in her meanness, and Amanda Seyfried is appealing as a young woman who thinks she is on a vacation to Mexico. She has no idea that, for her boyfriend, it’s a drug run.

Inconsistencies in character behavior undermine the storytelling throughout. When things are so glaring that they make you stop and say, “Hey, hold on a second, why did ...,” you know there are problems. Still, Oyelowo is quite abandoned in this, and he’s personable enough to make us keep caring about him long after we’ve given up caring about the movie.

Mick LaSalle is The San Francisco Chronicle’s movie critic. Email: mlasalle@sfchronicle.com

Gringo

Comedy-drama. Starring Charlize Theron, David Oyelowo and Joel Edgerton. Directed by Nash Edgerton. (R. 110 minutes.)