James Norton, the actor who fixed up so smartly in TV’s McMafia that he instantly jumped to the top of the list to take over from Daniel Craig as James Bond, looks completely different here, and it took me a while to place him. With his neck tattooed, face gaunt and pale, Norton plays Belfast window cleaner John, a single dad who is dying of brain cancer. The movie, inspired by actual events and directed by Italian film-maker Uberto Pasolini, is the story of John’s search to find a family to adopt his four-year-old son Michael (Daniel Lamont). It’s tender and poignant, but might be a bit cloying were it not for Norton, who underplays it beautifully with a performance of tremendous depth and empathy.

At the start of the film time is already running out for John, whose ex walked out when Michael was a baby. He has no family, so is working with social workers to interview prospective parents. It’s a definite “no” to the smug poshos and the couple who tell him they were hoping for a baby, but well, you know, beggars and all that. One or two of the couples are sketched as cartoonishly awful, which is a bit jarring. Where the film really comes alive is in the small details of everyday life – including one gorgeous moment as John walks Michael to school, the camera observing somehow both his heartache and pleasure holding hands with his son.

The film gets dangerously close to sentimental; what keeps it interesting is the acting. Lamont, who plays little Michael, is a natural. On the page John is ever-so-slightly cliched; he fits the stereotype of the saintly working-class character whose own difficult childhood seems to have left him virtually baggage-free, a heroic selflessly good parent. And yet in spite of myself I invested totally in Norton’s spine-tingling, intimate performance; and, in spite of myself, the end had me in floods of tears.

• Nowhere Special is released on 16 July in cinemas.