Jean-Pierre and Luc Dardenne offer another in their remarkable series of contemporary neo-realist dramas in this quietly devastating but gently hopeful portrait of a boy abandoned by his father who’s given a second chance at a family by an unassuming but innately decent young woman. The title of “The Kid With a Bike” obviously recalls one of the classics of the original postwar movement, Vittorio De Sica’s 1947 “Bicycle Thieves,” but in theme it also suggests one of the least realistic of all films, Charles Laughton’s 1955 masterpiece “The Night of the Hunter”—a marriage that would seem one of the unlikeliest in cinematic history but works brilliantly.

As is usual with the Dardennes’ films, the plot is simple but fraught with moral complexity. Cyril (played with an amazing combination of intensity and vulnerability by 13-year old newcomer Thomas Doret) has been placed in an orphanage outside the working-class Belgian town of Seraing by his single father Guy (Jeremie Renier). Assured by his dad that the stay would be a short one, Cyril will break any rule and take any risk to escape and reunite with Guy. But on one of his treks he finds that his father has simply moved. Before he’s taken back into charge by the orphanage staff, however, he literally bumps into Samantha (Cecile de France), a hairdresser, at a medical clinic. As he clings to her and the counselors pull him away, she reacts not with fear but simple, unaffected concern.

The next day Samantha turns up at the orphanage with Cyril’s beloved bike, saying she bought it from the father of another boy to whom his dad had sold it. Refusing to believe that his father would have sold his bicycle (they must have stolen it, he figures) but glad to have it back, Cyril abruptly asks the woman if she’d become his foster guardian during the weekends, and much to his surprise she agrees.

The remainder of the picture sketches, simply but powerfully, Samantha’s gentle but determined effort to help Cyril face reality and control his anger. That involves not only leading the boy finally to admit that his father sold his bike, but finding Guy and making him tell the boy that he has to give up his dream of coming back. But it also includes a struggle over Cyril’s soul between her and a neighborhood punk named Wes (Egon Di Mateo), who lures the boy into committing a robbery for him. The fact that she chooses Cyril over her boyfriend foreshadows an even costlier decision she makes when the consequences of the boy’s past intrude, in a final reel that posits a future less bleak than one often finds in the brothers’ pictures but still has some dark clouds obscuring the sunlight.

That’s visually characteristic of the film as a whole, with Alain Marcoen’s cinematography brighter, more vivid though no less deliberately “verite” than is the norm in the Dardennes’ work. But what really sells “The Kid With a Bike” are the performances of Doret and De France. With his restless movement and a piercing glare that reveals both wariness and neediness, he unaffectedly presents a heartbreaking picture of a waif whose chances are slim. She draws a portrait of a stern, sensible woman who just does the right thing, though she can’t articulate why she makes the choices she does—a younger, less verbal version of Lillian Gish’s Miz Cooper but one equally unwavering in her effort to protect her charge. The supporting cast is strong across the board, with Dardenne regular Renier again capturing the essence of a casually cruel man who can’t appreciate the implications of his choices and the others adding subtle nuances to decidedly imperfect characters (like the father-and-son who, at the close, go instantly from being simple victims to people desperate to avoid the consequences of their actions).

The naturalism of “The Boy With a Bike” casts an engrossing spell that’s punctuated at important turning-points by a simple orchestral phrase from Beethoven’s Fifth Piano Concerto that’s left hanging, unresolved, until the final credits, when Alfred Brendel’s rendition of the solo adagio enters to complete it. The musical effect complements the dramatic one the picture achieves with a final moment reminiscent of—but very different from—that in Truffaut’s “The 400 Blows,” about another boy caught up in the dangers of a damaged childhood. It leaves you sad at the cruelties of which men are capable, but also uplifted at the recognition of how powerful a force a simple act of kindness can be. Without preaching, the Dardennes have again delivered a message at once poignant and intensely relevant.