Agreeably shambolic, with a cast far funnier than the script suggests, “Lady of the Manor” is a ghostly comedy that comes apart more often than it comes together.

It feels and plays as largely improvised, with the improv lines rarely landing laughs.

Melanie Lynskey, Judy Greer and Ryan Phillippe seem so right in their parts that you’d think this comedy from writers/directors Justin and Christian Long could not miss. But it does, and more often than not.

Lynskey, seen recently in “Mrs. America” and “I Don’t Feel at Home in this World Anymore,” is Hannah, a Savannah (actually, Tampa/St. Pete) stoner/slacker vulgarian who barflies her way into a gig dressing as the lady of one of the historic city’s many manor houses, leading tours without memorizing any of the history she’s supposed to impart.

“Don’t worry, my ex-roommate used to watch ‘Downtown Abbey!'”

She spends a lot of time in her hoodie and pajama bottoms. She hits the pipe, a lot. She belches, stumbles, fumbles and swears, a lot, and finishes off each tour group with a farewell equally out of character.

“As Lady Wadsworth used to say, ‘You don’t have to go home, but you can’t stay here.'”

Part of the gig is that she gets to live in the house, owned by an old Savannah family whose patriarch (Patrick Duffy) is running for mayor and whose ne’er do well son (Phillippe) figures he’s entitled to sexual favors from his latest hire, Hannah. Hannah figures this, too.

And that’s what brings the ever-so-proper ghost of the original Lady Wadsworth (Judy Greer, perfect) out in protest.

She drawls out “trollop,” and exhortations about what “a lady” should “NEVER do.” Hannah isn’t having it. She seeks help with this “old fashioned BITCH ghost” from a history professor (Justin Long), hoping a supernatural sage “cleansing” can be arranged, even an exorcism.

“Not like (with) an old priest, but a hot, young like ATHLETIC priest who can really take a beating!”

Eventually, the ghost and the tour guide reach a rapprochement, and Lady Wadsworth starts prompting Hannah on the tours, giving her “lady” comportment lessons, bread making lessons and diction lessons — “Say it without laughing, DICTion!”

Greer’s snooty, elitist Old South drawl colliding with Lynskey’s dazed doltishness is the reason to see this. That’s not enough.

There is a “plot,” a mystery to be solved, played up as a third act afterthought.

Not filming in Savannah means the film feels unmoored from its “Midnight in the Garden/Forrest Gump” dripping, drawling drollery.

The script is thin on laughs that aren’t built on drugs, drunkenness and the lazy comic’s best friend, “dick” jokes. The Long brothers were aiming for something with a “Bridesmaids/Girls’ Trip” vibe — vulgar hilarity. Neither they nor their cast were up to that level of crude.

The leading ladies gave me a chuckle or two, but the poor dears were on their own. The writing-directing (and in Justin’s case, co-starring) Long brothers let down the side.

There’s no reason this cast with this story in this setting shouldn’t have been something almost hilarious. There’s little evidence on the screen that was ever going to happen.

Rating: R for language (profanity) throughout, sexual material and drug use

Cast: Melanie Lynskey, Judy Greer, Ryan Phillippe, Tamara Austin, Justin Long, Luis Guzman and Patrick Duffy

Credits: Scripted and directed by Christian Long and Justin Long. A Lionsgate release.

Running time: 1:37