If a biopic on Ernest Hemingway and Martha Gellhorn’s relationship includes a sex scene in the middle of a shelling, it cannot be deemed a complete failure. The HBO original movie that premiered last week, “Hemingway and Gellhorn” makes some of the right moves and has a bright cast, but even if you have an interest in these writers, the movie’s still merely passable.

Its heart is in the right place. By focusing on Martha Gellhorn, Hemingway’s third wife who was herself an accomplished writer, you’re telling the half of the story that ought to be told. At the breakout of the Spanish Civil War, Gellhorn meets Papa in Key West and accompanies him on the overseas assignment to Spain. She hooks up with Hemingway as a rival to the titan of letters, but as their romance sours, she eventually struggles to escape the titan’s shadow.

Nicole Kidman does a terrific job with Gellhorn’s maturation. Initially she’s a spitfire war correspondent merely in it to prove her machismo; as she witnesses wartime atrocities, she’s no longer drawn to conflict for the adrenaline rush but for the stories that need to be told. Consequently, Gellhorn finds her pissing matches with her famous lover to be less and less amusing.

I wouldn’t wish Hemingway on any woman, so Gellhorn’s understandably coming off the victim here. The movie is content to leave out her extramarital affair, among other blemishes, so some of that victimhood’s deliberately manufactured.

Fightin’ Round the World

It’s hard to make Hemingway into a caricature. I disliked his portrayal in Midnight in Paris only because he was the figure most lazily reduced to a collection of quotes, not because he was exaggerated. Having Hemingway randomly leap from his seat and shout “Who wants to fight?”– that’s not really an exaggeration.

Clive Owen’s not a charismatic actor, and likewise this is a disappointingly uncharismatic Hemingway. The pieces to Papa’s personality are there, from his grave sincerity to his boyishness to his shocking pettiness, but Owen can’t quite coherently resolve them.

Interspliced within the film is authentic black-and-white wartime footage. When a period movie incorporates old film like this, it’s normally sparing and between scenes. To accommodate these shots (which it uses a lot) Hemingway and Gellhorn drains its own film’s color for transitions.

It doesn’t work at all. Not only are these switches distractingly frequent and often pointless, the close-ups of Nicole Kidman and Clive Owen, no matter how grainy, aren’t fooling anyone as archival. And you can’t just insert them into iconic footage without the effect being laughable. What worked for Forrest Gump is pretty inadvisable here.

The last memorable bits to savor from this movie are the interesting supporting roles. Robert Duvall is a Soviet general, David Straithairn’s a great John Dos Passos, Peter Coyote shows up as my hero, the legendary editor Max Perkins, and is that filmmaker guy the drummer from Metallica? (He is.)

Is the casting silly in places? Sure. But that’s amusement I’ll take in a movie that’s otherwise underwhelming.