Four struggling L.A. actors retreat to a mountain cabin to write themselves some work via a zero-budget screenplay, but things take a meta-not-quite-horror turn in the Duplass Brothers’ follow-up to their “mumblecore” festival circuit hit, “The Puffy Chair.” Billed as a kind of comedy-horror film, “Baghead” starts out strongly, poking knowledgeable fun at the indie film scene, but takes way too long developing the uninteresting tangle of relationships, real and imagined, between buddies Matt (Ross Partridge) and Chad (Steve Zissis) and their respective not-exactly-dates, Catherine (Elise Muller) and Michelle (the ultra-cute Greta Gurwig of “Hannah Takes the Stairs”). By the time a seriously tipsy Michelle thinks she’s dreamed of a creepy slasher with a bag over his head, and that becomes the subject of the screenplay the foursome imagines they might work on, we’ve lost a great deal of interest. Even when an actual dude with a lunch bag over his head starts appearing, the dramatic juices never really flow. While “Baghead” eventually regains some steam, it’s pretty much the opposite of scary – and I’m rather easily scared – and not even close to funny or compelling enough to rate a recommendation, despite a sweet-natured ending, some laughs early on, lots of good intentions, and some very decent performances. It might, however, make an interesting point of comparison when the possibly-meta super secret Joss Whedon/Drew Goddard collaboration, “The Cabin in the Woods,” comes out next year.