A seedy-looking, longhaired Matthew Modine stumbles into his agent’s office looking for a “cause” that will bring him back from obscurity and get him invited to “A-list” parties again. How about if he adopts an Ethiopian orphan — that’s in Africa, right? Or becomes a spokesman for one of those “colored ribbon” diseases?

No, no, no, his agent ("Frasier"’s Peri Gilpin) tells him. That’s all been done. It takes her gay makeup artist and general factotum, Jeffrey (“Third Rock”’s French Stewart), to come up with a new idea. Apparently, an obscure tribe, the Chimborazzi of the Ecuadorian Andes, is threatened with extinction because their chief resource, the alpacas, are mysteriously dying off. So it’s Matthew Modine to the rescue!

Sounds like a fun premise for a play, doesn’t it? First-time playwright Blair Singer thought so. And so did director John Rando. But it was not to be. Singer’s writing is only occasionally funny and Rando’s direction is wooden and flat. And everybody’s timing is off.

Modine breezes through his role with ease and charm, and Stewart, playing two roles, has some of the best lines as the limp-wristed, tush-wagging gay — that is, if limp-wristed, tush-wagging gays strike you as funny. In his other role, as the U.N.’s High Commissioner for Refugees in Ecuador, he is not only superfluous, but unintelligible. What is that accent supposed to be?

Gilpin, as Modine’s agent and love interest, is undeniably beautiful and played her role amusingly deadpan because her face was supposedly so Botoxed that she couldn’t move any of it, but her sex scenes with Modine were awkward, unconvincing and lacking in emotion or heat. In fact, they weren’t even as convincing as the sex scenes between the last two alpacas left before extinction.

The saving grace of this production are the three Chimborazzi tribesmen, Abraham (Edward Padilla), Santos (Mark Damon Espinoza), and Angel (Reggie De Leon) whose bright red Guatemalan-style costumes and headgear are truly wondrous, thanks to designer Robert Blackman. These three have been waiting for the “prodigal son” to return and save the tribe. The prodigal son, according to tradition, has “three first names” and so Modine fills the bill, since his name is Matthew Moe Dean.

Mark Fite, as Modine’s conscience, is an entertaining diversion in a fantasy scene, and does fairly well as a tribal shaman, talking to Stewart in “ooga booga”-type language. (Making us long for Sid Caesar and Carl Reiner, who did that sort of thing for real.)

Another bright innovation, thanks to set designer Beowulf Boritt, is the overhead captions that introduce each scene, as they do at the opera. And, blessedly, the actors wear no visible mikes, so most of the dialogue is clear and audible.

If Modine truly wants to get back on the “A-list,” however, this is not the ticket to do it. Unfortunately, being Modine is not nearly as interesting as being John Malkovich.

“Matthew Modine Saves the Alpacas” will continue at the Geffen Playhouse, 10886 Le Conte Ave., in Westwood, Tuesdays through Fridays at 8 p.m., Saturdays at 3 p.m. and 8 p.m., and Sundays at 2 p.m. and 7 p.m. through Oct. 18. Call (310) 208-6500 for reservations.

Cynthia Citron can be reached at ccitron@socal.rr.com.