"Pterodactyls," which opened Saturday at the Source Theatre, is yet another spurt from the angst-swollen psyche of Nicky Silver ("Free Will and Wanton Lust," "The Food Chain"). Silver's plays don't really move from one plot point to another, they just roll onto the stage and explode, spattering the audience with rage, desperation, sorrow, shame and one-liners. "Pterodactyls" is soggy, though--a damp blast of complaint.

The production, which inaugurates Source's warmly intimate new space, is directed raucously by Michael Russotto and has a first-rate cast. Christopher Borg plays Todd Duncan, who, dying of AIDS, comes home to his upper-class family for a little peace and rest. What was he thinking? I mean, he grew up there--surely he knew. . . . But the audience doesn't know, and gets to discover that the Evil Mom (Kerry Waters) is a smothering alcoholic who emotionally crippled her son, and the Evil Dad (Conrad Feininger) is an uninvolved egotist who emotionally crippled his son and whose lustful, if unfulfilled, desires toward his daughter Emma (Katie Barrett) have traumatized her so that she can't remember most of her life, including the fact that she has a brother. Emma is hoping to escape by marrying innocent Tommy McKorckle (Jerry Richardson), but before you can say "campy and absurdist" he's donned a maid's uniform and moved in as the housekeeper.

The play certainly has some hysterical moments. Silver can get all his self-involved characters on the stage at once and then juggle them in more and more hilarious combinations. Their selfishness is so intense that they're spiritually blind, and they keep slamming into each other's feelings like bumper cars. The members of the cast are in high form and high spirits, their characters blithely recoiling from the impact and shooting away to inflict more damage.

Up until the end, when he judges himself along with his wretched relatives, Todd just wanders around the vulgar Duncan living room being smarter than everyone else and reconstructing the skeleton of a dinosaur that he's unearthed in the garden, a symbol the playwright has provided just in case the audience is too dim to figure out that this American family is dead, vanished, extinct, past its time, gone with the wind, down the drain, etc. Still, the audience can't help noticing that it's poor Todd, unrecognized, unremembered and ill, who manages to infect and kill one character and drive another to suicide. Todd's hatred is the motor that drives the plot, and if the play is about anything, it's about his revenge.

Neither director nor actor gives us any hint that Todd knows what he's doing. Is he in denial? A hypocrite? Poorly written? In the meantime, no sense is made of scenes like the one in which Todd viciously, graphically outlines his varied sexual experiences in order to shock and disgust Dad. The implication is that it's somehow Dad's fault Todd has AIDS, but if you follow that idea to its conclusion you're left with the unlikely scenario that had Todd's family only been accepting, he wouldn't have led such a richly Dionysian sex life--as if the latter were some kind of aberration caused by bad nurturing.

Nurturing must have been bad, though. You can tell by the way Silver treats the female breast. One of Todd's more loathsome memories is of his mother in a transparent bra. He could see her nipples! Ugh! Gross! Yuck! No wonder he never recovered. No wonder he uses poor stupid Tommy as a tool for delayed revenge, though on his sister's body rather than his mother's.

"Pterodactyls" is dispiritingly familiar, from its meant-to-be-outrageous jokes to its well-worn targets: Mormons, the Catholic Church, middle-class parents. Silver has always reworked the same mother-son territory, but in his other plays the humor was a boiling froth produced by a deep, sorrowing pity for the characters. The only pity in "Pterodactyls" is self-pity.

Pterodactyls, by Nicky Silver. Directed by Michael Russotto. Set, Jos. B. Musumeci; lights, Dan Covey; costumes, Susan Chiang; sound, Jim Stone; props, Elsie Jones. At the Source Theatre through June 27. Call 202-462-1073.

CAPTION: Pity party: Christopher Borg, Kerry Waters.