Lily Collins plays a wealthy, powerful family’s daughter who learns about their skeleton in the attic — actually hidden in a bunker in the woods of the family estate — in “Inheritance,” a lumbering thriller from the director of the Margot Robbie bomb titled “Terminal.”

Putting the ballerina-dainty Collins in any movie where physical throw-weight matters is always problematic. Here, she’s a Manhattan district attorney facing down corrupt billionaires and their high-priced lawyers in court by day, a manic daughter trying to keep the upper hand on a bigger, more motivated hermit her father enslaved in an underground lair decades before.

Put aside any issues with the film’s pacing, the public servant’s reluctance to do what seems like the obvious “right” and “legal” thing, and it’s just hard to buy Collins in many situations this movie puts her in. She’s easy to underestimate, to perceive as a lightweight, figuratively and literally.

It all comes to pieces for Lauren Monroe when her stern, high-expectations banker/father (Patrick Warburton) dies in the middle of her biggest case.

Daddy shafting her in the will, favoring her embattled Congressman younger brother (Chace Crawford), assorted charities and her mother (Connie Nielsen), doesn’t help.

But Daddy left Lauren a flash drive and a key. He won’t tell her, on his video message from the grave, his “secret.” But the key, and the location of the lock it fits will. It’s the source of “a secret you must carry to your grave.”

That’s where the bearded, soiled and miserable hostage who eventually tells her his name is “Morgan” is kept. Played by a barely-recognizable (FLAWless accent, mate!) Simon Pegg, this reluctant hermit locked away where even sunlight can’t find him has a tale to tell. And he takes his sweet time telling it.

Lauren, even with pressures closing in around her (court, media attention, her in-the-dark husband played by Marque Richardson and their little girl), can’t let herself panic or even feel any urgency about getting to the bottom of this crime and scandal-above-all-scandals.

Morgan? He’s desperate but apparently patient, a man who has held on, clinging to a memorized recipe for key lime pie, making petty demands when he realizes she’s not going to let him go on sight.

“My survival would be my revenge” on her father, he tells her.

Director Vaughn Stein takes forever to get this movie on its feet, and the slower he goes, the more Collins stands out as inadequate as his lead. We need to have lots of doubts about her actions and motivations, sense an inner resolve and toughness, see her doing the instant calculus of what she’s confronted with.

A faster-paced film might have given us at least the illusion of those, papered over with the urgency of “This will all blow up in my face any second now” that we never, ever feel in a movie about a situation that should throw our heroine into a rash, blind panic.

Rating: TV-MA, violence, profanity

Cast: Lily Collins, Simon Pegg, Connie Nielsen, Michael Beach, Chace Crawford, Marque Richardson and Patrick Warburton

Credits: Directed by Vaughn Stein, scripted by Matthew Kennedy. A Vertical release on Netflix.

Running time: 1:51