David Dawson, Emma Corrin and Harry Styles in My Policeman.

Harry Styles is a decent actor. He was great in Dunkirk, and he delivers strong work in My Policeman. Regrettably, the film’s script can’t match the power of his performance.

Styles plays Tom, an English policeman in the ’50s who dates and eventually marries Marion (Emma Corrin), a nice woman who is completely unaware that Tom is sleeping with their mutual friend Patrick (David Dawson).

The story shows that cast in flashback, with Linus Roache (Tom), Gina McKee (Marion) and Rupert Everett (Patrick) playing them 40 years later. Tom and Marion are still married, and she has allowed a crippled Patrick to stay at their place. We slowly find out all of the things that led to Patrick winding up in their back room—including a prison stay, a hard life and an eventual stroke.

It’s all rather rote and routine, like a bad soap opera. It’s also very, very flat and boring, with a bunch of miserable people acting miserably. There’s nothing surprising about what happens here, and everybody is bummed from start to end.

Styles and Dawson have zero onscreen chemistry, so their affair comes off as forced and unrealistic. Roache and Everett, playing the older versions, are a little more convincing, but they barely have any screen time together. The Marion character is just a plot device handled in predictable, stereotypical ways.

This was supposed to be a big acting year for Styles. He gives it his best shot in My Policeman, but that “star-establishing” performance is still in his future.

My Policeman is now playing at Mary Pickford Is D’Place (36850 Pickfair St., Cathedral City); Century at The River and XD (71800 Highway 111, Rancho Mirage); and the Tristone Palm Desert 10 Cinemas (72840 Highway 111, Palm Desert), while streaming on Amazon Prime.