When you write a book as unforgettable as Room, it’s practically a given that all your subsequent work will be compared to it. Emma Donogue’s latest novel, Akin, is a different sort of family drama, an intergenerational tale that spans cultures. But like her 2010 bestseller, Akin manages to find the sweet spot in a story about a traumatized kid. Once again, although in a completely different situation, Donoghue explores the crucial roles of nurture and stability in a child’s development. Once again, she also makes it clear that even in difficult circumstances, love can make all the difference.

When we meet 11-year-old Michael Young, he’s had a rough few years: His mother is incarcerated for possession and dealing, and his father has died of a drug overdose at the age of 26. When the maternal grandmother with whom Michael has been living also dies suddenly, his overworked social worker (Is there any other kind?) desperately explores the boy’s “kinship resources.” Scraping the bottom of the barrel, she contacts his great-uncle, Noah Selvaggio, a retired chemistry professor and childless widower on the cusp of eighty.

The social worker explains that if Noah can’t take him, Michael will have to move into a group home in East Flatbush, Brooklyn. And once he’s in the nightmarish system, she adds, it will be hard to get him out. But, but, Noah says. Among other objections, he’s about to leave on a trip to his birthplace, Nice, his first visit since his mother sent him to America in 1942 at age four – without her.

Of course we know that Noah will concede. Without his agreement, there would be no story (or a very different one). Rather than delaying his trip to France, Noah makes hurried – and rather improbable — arrangements to bring Michael along. And so Akin becomes an odd couple caper: The Stodgy, Genteel Old Man and The Tough, Foul-mouthed Kid.

Noah’s long-delayed return to Nice has been spurred by his discovery of a packet of nine mysterious photographs taken in 1944 by his mother during the Nazi Occupation. He hopes that this trip will help him make sense of them, and of his mother’s upsetting wartime abandonment. Noah knows that she initially stayed behind in Europe to care for her father, a famous photographer known as Père Sonne — a play on his surname, Personnet. But he suspects there were other reasons why she didn’t join her husband and son in America until Nice’s liberation from the Germans.

In other words, with Akin, Donoghue is aiming for much more than than just a quirky road trip adventure. It’s an overdue excavation of old wartime traumas by a man suddenly put in charge of a boy whose upsets are far fresher. Although marred by some heavy-handedness, her treatment of their double story grows on you.

Among other things, Akin is about learning curves. A recurrent theme is the danger of speculation and the tendency to jump to false conclusions based on partial information. It’s a trap that Noah falls into repeatedly — about Michael’s parents, and about his mother’s odd behavior during the war. Did she have an affair with a German? Worse, was she a collaborator? An informer? Noah toys with multiple scenarios, many of which are implausible even to him.

Donoghue has written several historical novels, including Frog Music (2014), which was based on the true story of a 19th century cross-dressing frog catcher who was murdered. But while Akin has historical aspects involving an actual Resistance group that saved hundreds of children from the Nazis, its central focus is contemporary: Noah’s role in saving one child – Michael – from a different form of incarceration. Donoghue’s use of posthumously discovered photographs to answer questions Noah never asked during his mother’s long life recalls Penelope Lively’s novel, The Photograph (2003), in which a widower is driven to re-consider his deceased wife after he finds an incriminating picture that suggests she had an affair with her brother-in-law.

Donoghue plays up the irony that Noah, despite his education and august age, is more naïve than rough-edged Michael, who has been brought up in the school of hard knocks. Noah is constantly taken aback by the harsh realities of Michael’s world: “It hit him now that when a mother was sent to jail, her kids were receiving just as long a sentence,” Donoghue writes. Duh. It also occurs to him that rough neighborhoods like the one in which Michael has been raised are “like living under siege.”

Traveling with Michael, at least at first, is also somewhat like living under siege – for the reader as well as Noah. Unlike the compliant, sweet little boy in Room, Michael first presents as an unpleasant brat glued to video games on his cracked cellphone. Meals are an ordeal. “I want a Coke, motherfucker,” he snarls, testing his new guardian on their first outing. When Noah offers to buy him espadrilles after he befouls his beloved Nike Jordans in dog mess, “Michael gave him the finger and stomped away.”

As they traipse around Nice, an appealing portrait of this Riviera playground at Carnival time emerges in stark contrast with reminders of Nazi roundups and atrocities. Their itinerary includes rocky beaches, the circus, Père Sonne’s gravesite, and the Museum of the Resistance.

Photographic themes — focus, point of view, trompe l’oeil — help frame the narrative. Michael documents their trip with hilariously macabre selfies (and one sweet “ussie” of Père Sonne’s disparate descendants flanking his grave), but it turns out he’s also paying attention to his great-uncle’s lectures. He repeatedly picks up on clues to Margot’s pictures that Noah has missed. Heartwarmingly, in this book about filling in gaps and making connections, Noah doesn’t miss signs of Michael’s promise. Yes, Akin turns unabashedly sentimental, but only a stone wouldn’t be moved by its final pages.