Brendan (Joseph Gordon-Levitt) tries to solve the disappearance of his ex-girlfriend Emily (Emilie de Ravin) in “Brick.” The movie opens Friday at the Athena.

Here’s the skinny: The shamus gets a hot tip on the line from a dame who heeled a few weeks ago and sounds like she’s dosed. If he can get a lead and try not to gum it, finding her should be duck soup so long as the bulls don’t get involved.

That’s the setup of “Brick.” It’s an homage to old detective movies that has the logic, characters and – most obviously – lingo of a 1940s film noir. And the only twist we get before the movie is the fact that it takes place in a present-day California high school and hardly any characters can legally buy cigarettes.

At this high school, something is brewing, but — homage may it be — “Brick” is no “The Taming of the Shrew” by way of “10 Things I Hate About You.” In the film’s first scene, Brendan (Joseph Gordon-Levitt) crouches in a storm sewer, staring at his ex-girlfriend, Emily, dead and lying face-down in the water. Flash backward two days and he’s standing in a phone booth listening to her rattle off an incomprehensible stream of Mad Lib-esque dialogue.

Brick? Tug? Frisco? Pin? They don’t really make sense together, but Brendan is smarter than the average bear. He knows the secret to Emily’s disappearance lies therein, and off he goes to shake things up.

From there, “Brick” takes the slowly unfolding structure of the old detective movies director Rian Johnson reverently admires. Brendan sneaks into parties, puts the tough questions to drugged-up thugs behind a coffee shop and uses blackmail as the timeless tool that it is. He runs into dames with a secret or two lurking beneath those mascara-slicked eyelashes and isn’t afraid to scuffle with a jock in the parking lot.

One by one, Brendan is putting together the pieces of the puzzle, but “Brick” is more about the atmosphere than the clues. The myriad of locales that Brendan navigates are lit in ominous, seductive tones and cinematographer Steve Yedlin can make a deserted hallway of lockers feel like a rain-slicked city street.

As Brendan, Gordon-Levitt is beyond a perfect choice for the “private eye” part — he makes the movie. With his rolled-up jeans, spit-shined dress shoes and a mournful stare that can break into a fury at any given moment, he is Humphrey Bogart with a heart and bifocals.

“Brick” is so outstanding in some respects that its plot – or what we can piece together of it – is what hurts it. With so many different pieces of the puzzle to find, the movie tends to plod along too slowly, and some of the snaky — albeit entertaining — lingo in the film is hard to follow. But really, “Brick” is as much about solving the mystery of the disappearing ex as “The Maltese Falcon” was about a Maltese falcon.

And that’s what makes detective movies like these so entertaining despite their tenuous logic. This is not a movie about Emily, but about all of the shady deeds and backstabbing that add up to her death. What makes “Brick” even more enthralling is that everything adds up to an entirely different conclusion, a simple but devastating one that takes place on a lonely grass field. A question is answered, but it’s hard to remember what the question even was.