The first few episodes of HBO’s “Doll & Em” operate as a fairly funny show-biz satire, but then the series takes a nosedive into turgid melodrama.

Dolly Wells and Emily Mortimer of “Doll & Em” Photo: HBO

by Gerald Peary

For Doll & Em, a tonally shaky six-part comedy series debuting this month on HBO, off-screen best friends, Emily Mortimer and Dolly Wells, are both the co-writers and Brit leads, playing send-up versions of their real selves. The premise is appealing: Mortimer (“Em”), comes to the US to star in a film. She invites along her bosom pal, Wells (“Doll’), because Doll is raw and deflated from breaking up with her long-time boyfriend. Em has a plan. Doll could get a hefty studio check while they hang out in LA, if she agrees to be Em’s “assistant.”

Doll signs on, they move in together in La la land. “Should I make coffee or tea, or something?” Doll inquires in the first episode, as they lounge together on separate couches. Em insinuates that she doesn’t expect her pal to really do much assisting. But still, if Doll were to bring her coffee (she would never ask Doll to do it!), Em does like, she says, “a frosty latte…three shots…in a medium-sized cup.”

Pretty amusing, right? The inflated celebrity. In episode two, Dolly, gone swimming, gets locked outside of Em’s rented estate for 12 awful hours, shivering in a bathing suit by the enclosed pool. When she ventures home, Em barely notices Dolly’s hysteric misery, as she’s fatigued after demanding hours on the movie set: ”Well, I guess we both had bad days.”

For a time. Doll & Em operates as a fairly funny show-biz satire with Em the self-deluded prima donna. I expected the series to continue this way, and the humor would come from the thousand ways Em lorded over her friend as assistant, pulling rank and taking advantage, while declaring that she and Doll are equals. But no, Doll & Em weirdly shifts and changes around episode three. Em loses her mojo, and it stays lost until the end. Suddenly she’s hesitant and ineffectual, whimpering and cowering, and, worried that, at age 40, her acting career is almost over. She does slow burns and petulantly slams doors. “I’m so so sorry” is her mantra.

Unconvincingly, Doll emerges as a snippy, sneaky Eve Harrington from All About Eve, ever undermining her best friend, somehow becoming the most popular person on the production. And with sudden ambitions to be a screen actress herself. (Here is one departure from reality. Bridget Jones’s Diary’s Wells plays Doll as a non-thespian, who works back in London in a restaurant.)

It’s hard to screw up scenes on a movie set, when famous actors as themselves pass through for self-parody cameos. Doll & Em is funniest when Doll is pursued by an enraptured John Cusack, when Andy Garcia arrives to seek out an “assistant” for himself, when, very delicious, Susan Sarandon moves from shrill, self-righteous moralizer to, upon toking up, licentious stoner. Some less-famous actors are effective also, including Jonathan Cake as a womanizing producer and Aaron Himelstein as the serious-minded but foolish-speaking film director.

But then, alas, there are episodes five and six, which change again the thrust and tone of Doll & Em, this time fatally. What had been lightweight comedy becomes, at the end in the USA, turgid melodrama. Then, back In England, dreary, phony schmaltz.

Check out Wells and Mortimer, so wonderful, respectively, in Morvern Callar and Lovely and Amazing. But I predict no season two for their Doll & Em.

Gerald Peary is a professor at Suffolk University, Boston, curator of the Boston University Cinematheque, and the general editor of the “Conversations with Filmmakers” series from the University Press of Mississippi. A critic for the late Boston Phoenix, he is the author of 9 books on cinema, writer-director of the documentary For the Love of Movies: the Story of American Film Criticism, and a featured actor in the 2013 independent narrative Computer Chess.