Shannon and Ryan own the screen in "The Missing Person"

It doesn’t happen often, but it’s always thrilling when a performer you’ve never seen or just never took much note of makes such a strong impression that you think “Who is that?!”

One such moment occurred two years ago, when Ben Affleck’s shockingly good directorial debut Gone Baby Gone featured a live-wire Amy Ryan as the missing girl’s abrasive, rather appallingly unfit mother. Another came last year, when Sam Mendes’ Revolutionary Road had scenes stolen whole from hardworking stars Leonardo DiCaprio and Kate Winslet by Michael Shannon, playing the mentally unstable neighbor’s son who nonetheless sees straight through the lies of their marriage.

Both actors were hardly newcomers—Ryan has acted on Broadway (winning two Tony nominations), TV (including semi-regular gigs on The Wire and more recently The Office) and in movies. Shannon had been arresting before, albeit mostly in small parts and/or movies relatively few saw like Bug, Let’s Go to Prison and Shotgun Stories. But these particular roles made them seem like actors one absolutely needed to see a lot more of from now on.

Which seems to be working out just fine: Shannon stars in Werner Herzog’s new My Son, My Son, What Have Ye Done” (purportedly even weirder than his *Bad Lieutenant) and plays Humbert Humbert-like music impresario Kim Fowley in the Runaways biopic premiering at Sundance next month. Ryan co-stars with Philip Seymour Hoffman in his forthcoming directorial bow Jack Goes Boating, then has the female lead in Green Zone, the next Matt Damon/Paul Greengrass collaboration.

But meanwhile, both of them are in the contemporary indie noir The Missing Person, which opens next Friday. A barbed, bizarre, blackly comedic little Christmas present it is.

Writer-director Noah Buschel’s prior features Bringing Rain and Neal Cassady (the latter with Ryan as Carolyn Cassady) were not particularly well received. But this third effort is serpentine, smart and full of surprises. Plus it’s got Shannon and Ryan, who of course are terrific.

He plays John Rosow, a Chicago private dick first met in classic noir circumstance: Getting wee-hours call from a mysterious new client, waking badly hung-over in his dilapidated office’s fold-out. Offered more money than he can refuse, he groggily boards the California Zephyr train to tail a subject who appears a pederast traveling with a Mexican juvenile.

But appearances deceive throughout a narrative that ultimately, meaningfully folds in personal tragedies related to the World Trade Center, human trafficking, FBI investigation, classic jazz appreciation and more—all the while retaining a sharp sardonic edge.

Much of that is due to Shannon, an actor who seems incapable of doing anything entirely expected. Not conventionally handsome, as quirky as Nicolas Cage without the show-off aspect, sunk deep into dysfunctional character, he’s quietly genius here. (There are also numerous wonderful support turns, particularly John Ventimiglia’s as a cabbie.)

As the hiring client’s terse intermediary, Ryan gets less to do than one might expect, given her executive-producer credit. Much of her role is spent on the phone, ragging our hero long-distance. Still, she owns the screen when she’s on it.

The Missing Person arrives at something much more depthed than its neo-noir mystery format initially suggests. It’s a rather fascinating movie that transcends genre homage, as the Coens’ Blood Simple, Robinson Devor’s “The Woman Chaser” and Richard Shepard’s The Matador did.

Not that those fellow neo-noirishly angled features are anything alike. Yet all share a deep-dyed yet organic narrative unpredictability, stylish directorial confidence and supreme belief in exceptional lead actors that The Missing Person echoes, with an extra final dose of unironic heart.