A family gathers at the parents beach house for a not-quite-holiday get-together in “Blackbird,” a downbeat but arresting and intimate melodrama based on the Danish film, “Silent Heart.”

Daughters Jennifer (Kate Winslet) and Anna (Mia Wasikowska) and their families are here for an early Christmas with Mom (Susan Sarandon) and Dad (Sam Neill). They “celebrating” now because mother Lily won’t be around Dec. 25. She’s terminally ill.

And at the end of this weekend, she’ll be taking a drug cocktail that ends her life, while she still has the capacity to do that on her own.

Sarandon’s Lily is a feisty sort. None of this soothing classical music that husband Paul prefers. Oh no. She’s aware of how long it takes her to get a bathrobe on, and doesn’t want to be hovered over as she does.

“Go f—–g DO something,” she barks, for not the last time. Lily is out of patience and almost out of time.

Organized adult daughter Jennifer is aware that she’s in pain, because “She lies just badly enough that you know she’s lying.”

Her pedantic husband Michael (Rainn Wilson) can make historical anecdote small talk with the best of them. Pass the salt.

“You know the Indian independence movement started” with salt protests, he begins. It’s no wonder Jennifer’s testy, “fragile” younger sister Anna calls him “Mr. Dull.”

She has her own issues, which Jennifer lists for her every moment she gets her alone.

Lily’s best friend (Lindsay Duncan) is here for support. But only Jennifer and Michael’s doted-on/nagged to excellence teen son (Anson Boon) has the tactlessness to be direct.

“When’s it happen?” And later, with his grandpa, a stoic pillar of equanimity, he’s even more blunt.

“How’re you going to do it?”

Director Roger Michell (“Venus,”Notting Hill”) cast this well and earns stellar on-the-nose performances from Sarandon, Wilson, Duncan and Wasikowska. Pairing her opposite Winslet turns out to be inspired, as their characters are highly-strung flipsides of the same coin, making for some splendid fights. Each knows where to stick the dagger.

Sarandon’s Lily has the sarcastic bravado common to end-of-life movies of this sort, from “Whose Life is It Anyway?” to “Me Before You.”

“You up yet?” she shouts at the kids. “I’d DEAD soon. You coming down?”

Neill’s Paul might be the most accessible character, simply by virtue of his “get through this with a little ordinary grace” ethos. But how are YOU doing, Paul?

“A little tired of people saying ‘And how are you?'”

The conflicts come from the usual corners, the twists have a pre-ordained feel. But the players, the setting (West Sussex, UK, doubling for Long Island?) and Michell’s sure-handed way with sensitive material get “Blackbird” airborne, and keep it there, from beginning to not-remotely-bitter-end.

MPAA Rating: R for language, some drug use and brief sexual material

Cast: Susan Sarandon, Kate Winslet, Mia Wasikowska, Sam Neill, Rainn Wilson, Bex Taylor-Klaus, Anson Boon and Lindsay Duncan.

Credits: Directed by Roger Michell, script by Christian Torpe. A Screen Media/Fathom Events release.

Running time: 1:37