Ordeal by Innocence (2018)

This is an adaptation of an Agatha Christie book, set in the era it was published, more or less, which is the late 1950's.  The sensibilities are still a bit old fashioned, with things like sex before marriage and divorce the sort of things that you wouldn't talk about at all, not just in social gatherings.
Here’s the plot in brief: It’s Christmas Eve and wealthy philanthropist Rachel Argyll (Anna Chancellor) has just been murdered. Suspicion immediately falls onto her son Jack (Anthony Boyle), one of five adopted children that Rachel and her husband, Leo (brilliantly played by Bill Nighy), have taken into their home and raised. Despite claiming innocence, Jack is quickly swept off to prison, where it doesn’t take very long for him to succumb to a fatal beating. The family is just vaguely beginning to recover from this double tragedy 18 months later, when, a shabbily dressed man (Luke Treadaway) arrives at their door with a beat-up suitcase, an uncomfortable, stammering manner, and what he thinks will be good news: He can provide an iron-clad alibi for Jack at the time of Rachel’s death.  That’s understandably unsettling information for Leo and his surviving kids—bad boy Mickey (Christian Cooke), youthful rebel Hester (Ella Purnell), taciturn Tina (Crystal Clarke), and high-strung Mary (Eleanor Tomlinson)—since if Jack didn’t kill their mom, it means one of them probably did.  And so it goes to the end.