Casey Affleck and Michelle Monaghan in “Gone Baby Gone.”

Up, up, and away.

Ben Affleck had already played Superman. In 2007 in “Hollywoodland.” Now, without the cape and tights, he just seemed like one as the producer, director, and co-writer of “Gone Baby Gone.”

It then became obvious that there was an impressive and promising new moviemaker on the scene as well as an equally impressive and promising star.

And you already know their names: Affleck.

Any whispers of self-indulgence or nepotism would soon be gone baby gone.

Ben, making his directorial debut (one so assured and effective, you found yourself thinking that directing just might be his forte and destiny, which became even more evident a few years later when he turned out the masterful “Argo”), directed his younger brother Casey, who plays the protagonist.

Each knocks the ball out of the park.    

“Gone Baby Gone” is a twist-and-turn-filled mystery-drama, a kidnapping thriller based on a novel by Dennis Lahane, who wrote the novel that would be adapted into director Clint Eastwood’s superb thriller, “Mystic River.”

Both Boston-set movies focus on working-class realism and both reverberate thematically with narratives that involve missing children, the search for justice, and the gray area that houses elements of both right and wrong on the ethical and moral spectrums.

Casey Affleck and Michelle Monaghan play private investigators, partners at work and at home. When the four-year-old daughter of drugged-out mom (and Oscar nominee) Amy Ryan disappears from Boston’s tough Dorchester neighborhood, the pair of PI’s take on the high-profile missing-child case.

This brings them into contact and conflict with a police captain (Morgan Freeman) and a police detective (Ed Harris), who reluctantly agree to have the PI’s tag along.

Virtually every character comes to reveal aspects not readily apparent, and the case takes the principals down alleys and around corners that neither they nor anyone else see coming at the outset.

Baby-faced Casey is terrific — even stronger than in his Oscar-nominated supporting turn in “The Assassination of Jesse James by the Coward Robert Ford” — with a compelling mix of decency and toughness that rings very true indeed. 

And his older bro’s first foray into directing resulted in a marvelously melancholy, superlatively suspenseful, thoroughly thought-provoking crime thriller.

“Gone Baby Gone” is fine baby fine.

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