New York playwright Christopher Shinn writes rat-a-tat dialogue. Like David Mamet, he depends on the listener to fill in the blanks between the lines. Motivations and mysteries clamor for attention in the pauses. A case in point is “Dying City,” which premiered in March 2007 at Lincoln Center Theatre. Staged by Cygnet Theatre’s associate artistic director Francis Gercke, the West Coast premiere is seen at Cygnet’s Rolando venue through Oct. 26. The action, set in January and July of 2004, takes place in New York psychotherapist Kelly’s Lower Manhattan apartment, from which, as newlyweds, she and her husband Craig watched events of 9/11, sitting on the sofa and holding one another. At curtain, the obviously depressed Kelly is packing Craig’s books and watching TV. A sheet and a pillow are stuffed into a corner of the sofa, indicating that may be where she’s slept since the military arrived unannounced to deliver the news of Craig’s Iraq death, the exact cause of which is a mystery. The bell rings. Kelly (Christy Yael) starts. It’s her gay brother-in-law Peter (Sean Cox, who also portrays Craig), whom she hasn’t seen since the funeral. He is Craig’s identical twin. An actor, he’s just walked out after Act I of “A Long Day’s Journey Into Night,” in which he portrays Edmund, the dying son. In scenes that alternate between Kelly’s last evening with Craig and her present conversations with Peter, the audience learns bit by tantalizing bit about their families and interpersonal relationships, each with the other and the others. And yet, each has secrets that are for us to decipher after the curtain falls. In subtle ways Cox differentiates his twins, though there is little evidence in Shinn’s script of the camaraderie that Kelly and Peter shared. Craig is the more perplexing man, and yet Peter is so complex and needy. As for Yael, one still anticipates her breakthrough into something different from the moist-eyed neurotics she plays so easily. There were hints of something more in Compass’ recent, wonderful “Three Days of Rain.” Without question, Shinn is a young playwright to watch. His “Dying City” is another example of those chewy kinds of plays Cygnet loves, plays that leave one to explore character, culpability, mystery and motivations, and to question the deeper meaning of whatever the heck that was. Whatever that was, the subject could not be timelier. Credit is due to Gercke for the brilliantly ironic television news finale (sound design by Matt Lescault-Wood, lighting design by Eric Lotze). “Dying City” continues at 7:30 p.m. Wednesday, 8 p.m. Thursday through Saturday, and 2 and 7 p.m. Sunday at Cygnet’s Rolando stage, 6663 El Cajon Blvd. No. N. For information and tickets, call (619) 337-1525 or visit www.cygnettheatre.com.