You know those “Saturday Night Live” skits that start out with one really clever idea, get a couple good laughs and then meander to an indistinct ending? “Marisol,” the latest from the Shard Live Performance Collective, is like one of those skits. The play’s first act and a half are as ferocious, funny and in-your-face as you can expect theater to be in this town. Director Richard St. Peter maintains a precarious balance between fractured reality and surreal nightmare. But in the final few scenes “Marisol” devolves into an absurdist ramble with mytho-poetic aspirations that never quite pan out. The play tells the story of a young Puerto Rican, Marisol (Gypsy Pantoja), who is warned by her guardian angel (Tiza Garland) that “God is old and dying and he’s taking the rest of us with him.” The battle that ensues between the angels and God obliterates the world as we know it. Marisol fumbles through the wreckage, looking for her best friend, June (Lara Brier St. Peter), and trying to avoid homicidal maniacs along the way. Playwright Jose Rivera does well when he balances his violent tendencies with deft touches of whimsy (one indication of the apocalypse: the French are now polite). But when Rivera turns heavy-handed, it’s up to St. Peter’s skillful cast to find the humanity in the oblique bluster. They’re certainly up to the challenge: Pantoja is radiant as Marisol, infusing her with a courageous perseverance. Garland makes a perfect modern-day angel-with-attitude: yelling, smoking and swearing, but also supremely caring. Martin Montgomery gets to chew the scenery as June’s demented brother Lenny, and he makes the most of the opportunity St. Peter employs a top-notch technical crew, resulting in more polished lighting and sound designs than normally seen at the Firehouse Theatre. But all the fine work can’t stop “Marisol” from being only three-quarters of a good play. “Marisol” runs Thursday-Saturday at 8 p.m. at Firehouse Theatre through Jan. 29. Tickets are $10; $6 for students. Call 306-8600 for