Katie Kleiger plays Mary Bennet and William Vaughan is Arthur de Bourgh in “Miss Bennet: Christmas at Pemberley,” running through Dec. 18 at Round House Theatre. (Grace Toulotte)

It is a truth universally acknowledged that a theater aspiring to community goodwill, not to mention a dependable income stream, must be in want of a holiday show. If said show can be a family-friendly piece with a feel-good vibe, so much the better. This principle helps explain “Miss Bennet: Christmas at Pemberley,” an underplotted Jane Austen pastiche that has landed at Round House Theatre for some vigorous but synthetic wassail.

Written by Lauren Gunderson and Margot Melcon, the comic “Miss Bennet” is a sequel to “Pride and Prejudice” and features versions of many characters from that novel. In other words, the play has a literary pedigree and aura of safe familiarity that might almost have been calculated to knock “A Christmas Carol” off its perch as most-favored yuletide programming choice. No surprise, then, that multiple theaters across the country are giving early stagings to “Miss Bennet” in the phenomenon known as a “rolling world premiere.” On opening night, Round House audiences certainly seemed won over by this production, directed by Eleanor Holdridge.

Brandon McCoy (Charles Bingley), left, William Vaughan (Arthur de Bourgh), center, and Danny Gavigan (Fitzwilliam Darcy) in “Miss Bennet: Christmas at Pemberley,” a holiday sequel to Jane Austen’s “Pride and Prejudice.” (Grace Toulotte)

The tale unfurls at Pemberley, ancestral home of Fitzwilliam Darcy (Danny Gavigan), the snobbish but handsome gentleman whose romance with the spirited Elizabeth Bennet was chronicled in “Pride and Prejudice.” It is now two years later, and Elizabeth Darcy (Erin Weaver) and her husband are hosting Christmas for their extended family. Among the guests is Elizabeth’s younger sister Mary Bennet (Katie Kleiger), no longer the pompous pedant we met in “Pride and Prejudice” but still of a scholarly bent.

So when Mr. Darcy’s aristocratic but socially bumbling bookworm cousin, Arthur de Bourgh (William Vaughan), also shows up for the house party, resulting in comic awkwardness and mix-ups, including confusion over copies of Jean-Baptiste Lamarck’s “Philosophie Zoologique,” which both Mary and Arthur are reading — well, you can see the rest of the plot coming down the elm-lined pike. Gunderson and Melcon throw some halfhearted plot twists in the way of immediate resolution, but the obstacles tend to fizzle, and the story’s comic and dramatic situations don’t always seem fully realized. Meanwhile, a couple of running jokes are milked to the point of exhaustion. For instance, there are incessant double takes at the sight of the Darcy family’s first Christmas tree. (Elizabeth is apparently an early adopter of the tree-decorating custom, gaining currency in England around this time.)

From left, Erin Weaver (Elizabeth Darcy), Katie deBuys (Jane Bingley), Katie Kleiger (Mary Bennet) and Miranda Rizzolo (Lydia Wickham) in “Miss Bennet: Christmas at Pemberley.” Kendra Rai designed the period frocks. (Grace Toulotte)

A degree of narrative diffuseness proceeds from the play’s sizable cast of characters, who admittedly allow audiences the fun of recognition and foible-spotting. (Theatergoers who have recently reread “Pride and Prejudice” may be best positioned to catch the script’s humor and allusions.) Upon emerging from the crowd, some of the personalities prove vibrant and funny. Most notably, Vaughan’s Arthur is adorably and hilariously hapless, and Kathryn Tkel’s Anne de Bourgh is a diverting typhoon of hauteur. Weaver endows Elizabeth with wry feistiness, and Miranda Rizzolo is aptly giddy as Lydia Wickham. Kleiger’s Mary displays some wonky charm, such as when she is entreated to cheer up while she performs thunderously on the piano. “I’m not upset!” she barks. “Beethoven’s upset!”

Kendra Rai designed the period frocks and other costumes, which show up to advantage on Daniel Conway’s set, with its parquet floor and chic furniture. The costumes may particularly cheer audiences still in withdrawal from the dress-ogling opportunities of “Downton Abbey.” You have to take your enjoyment where you can find it.

Miss Bennet: Christmas at Pemberley, by Lauren Gunderson and Margot Melcon. Directed by Eleanor Holdridge; lighting design, Nancy Schertler; sound designer/composer, Matthew M. Nielson; props master, Kasey Hendricks; dialect coach, Melissa Flaim; assistant director/dramaturge, Gabrielle Hoyt; associate sound designer, Justin Schmitz. With Katie deBuys and Brandon McCoy. About 2 hours. Tickets: $10-$70. Through Dec. 18 at Round House Theatre, 4545 East-West Hwy., Bethesda. Call 240-644-1100 or visit roundhousetheatre.org.