THEATER REVIEW : A Tangled Conventional Crime Yarn : Mix of theater art and gunplay in ‘Earth and Sky’ doesn’t quite work.

Playwrights tend to ignore genre material--that’s reserved for the moneymaking ventures in film and television, which support their playwriting habit. For many of them, genre stuff tends to bring up too many bad memories of too many bad story conferences.

Perhaps that’s why, when a playwright writes a genre play, it ends up something like Douglas Post’s “Earth and Sky” at Actors Forum Theatre. Like its central couple, Post’s drama is split between poetic ruminations and street-level toughness. It aims for theater art and gunplay, a little embarrassed to be just a conventional crime yarn.

Yet that’s all “Earth and Sky” really is. It even contains the kind of frantic wrap-up and twist typical of thriller teleplays--which Chicagoan Post has written.

He tries to involve us in something we can never quite buy into. Poet-librarian Sara (Molly Maslin) wants to find out who killed her lover, a shady restaurant owner named David (Richard D’Alessandro). We want to know what the intellectual, contemplative Sara ever saw in the slightly rough, crude David. Her passion for solving his murder extends from her passion for him, but her emotional drive beggars credibility.

While Post constructs the murder mystery narrative so straightforwardly that it reads like a how-to outline on genre writing, he intercuts this with Sara and David’s affair, told in reverse time like Harold Pinter’s “Betrayal.” It works as more than a device, since this is Sara’s memory ticking off the days and weeks spent with David. It also provides “Earth and Sky” with a stylishly calm coda.

Alas, this romance-in-reverse doesn’t show us anything. Instead of giving them time together so we can see the affair in action, Post has David tell Sara, in flashback after flashback, that he has to go. This is love on the run with a lot more run than love. Even that genre essential--the torrid love scene--is missing.

More awkwardly, Post turns Sara into an amateur sleuth who is told by everyone around her what we already know--she’s crazy to go up against David’s killers. As Sara inches closer to her prey, she unintentionally resembles someone who is obsessively myopic rather than the sympathetic heroine we first met. The final plot twist owes a lot to the tradition of corrupt Chicago politics, but it’s hardly startling.

Under Larry Lederman’s direction, the dramatic coil doesn’t tighten the way it should. Maslin gives Sara an alluring thoughtfulness, but can’t get past the script’s limits and clue us in on Sara’s attraction to David. D’Alessandro clues us in even less with a thin portrayal that’s lacking both sexual heat and a tough-guy edge. As Weber, the investigating cop, Richard Ruyle is good at oozing male scumminess while suggesting a guy on the verge of burnout.

The black, shadowy, Abstract Expressionist set by Dave Dunning, with John J. Grant’s pinpoint lighting, conveys more danger than the play finally does. So does Jerry Sider’s sound design, which pumps up Chicago’s cacophony.

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WHERE AND WHEN

What: “Earth and Sky.”

Location: Actors Forum Theatre, 10655 Magnolia Blvd., North Hollywood.

Hours: 8 p.m. Friday and Saturday, 7 p.m. Sunday. Ends Sept. 10.

Price: $15.

Call: (818) 506-0600.