WONDERSTRUCK Like “Thunderstruck,” but way quieter.

Todd Haynes has been in the zone for quite some time now, creating a remarkable streak of films that establish glorious illusions, and then burrow deeper for the real, messy deal. Wonderstruck, the director’s first movie for a younger audience, feels like an anomaly in other, less intriguing ways—including an atypically slack narrative and an occasional case of the cutes. But then the third act kicks in, and everything gets terrific.

Adapting a book by Brian Selznick, the story starts off in the ’70s with a young Minnesotan boy (Oakes Fegley) struggling to cope with the loss of his mother. After a freak lightning strike leaves him deaf, he runs away to New York to find his mysterious father. As clues inexorably lead him toward the gargantuan American Museum of Natural History, the movie keeps flashing back 50 years, zooming in on a hearing-impaired girl (Millicent Simmonds) with a similar tie to the landmark.

Few directors can find the texture in a timeframe like Haynes, and his depictions of multiple eras of New York are lived-in triumphs, transitioning between gorgeous black and white and faded Scorsese scuzz at delightfully random moments. (Carter Burwell’s constantly morphing score makes a strong bid for MVP.) Unfortunately, the backdrops often tend to overshadow the actual goings-on: Charming as the young performers are (newcomer Simmonds is a particular find), the lengthy sequences of them traipsing through various exhibits come off as maybe a bit less entrancing than intended.

Once Wonderstruck’s stories finally sync up, however, it’s possible to forgive quite a bit. Set within the Queens Museum’s astounding model of New York, Wonderstruck’s finale finds Haynes in top form, depicting loss, memories, and hope in a way I don’t think I’ve ever seen before. Sheer movie magic should never be discounted, even when it takes a while to arrive.