Usually, when a story starts with a celebrity and a devoted fan, it ends with a death or two and maybe someone being driven off in cuffs. So it’s refreshing to encounter Marthe (Laura Giannarelli), a middle-aged woman with a smart red suit, a quick mind, and a fondness for novelist Paul Parsky that’s at once reverent and teenybopperish but nowhere near Mark David Chapman territory. She’s never met Parsky, but she thinks of reading each of his books as “embarking on an intimate relationship” with him. When fate places Parsky (Bill Largess) in the facing seat of her compartment on a Paris-to-Frankfurt train, we know that something will happen. It’s difficult to write about the Washington Stage Guild’s production of The Unexpected Man, Yasmina Reza’s follow-up to the critically lauded Art, without spoiling the deliciousness of what does happen. Suffice it to say that most—but not all—of the dialogue takes place in the minds of Parsky and Marthe as the train hurtles through the darkness. Upon recognizing her companion, Marthe begins talking to him—not directly, mind you; he’s scarcely noticed her. “I’ve spent my life with you,” she reveals breathlessly, then tells how her late friend Serge, who hated Parsky’s books, said that “your greatest gift was making me love you.” But what of the celebrity artist’s mind? What does Parsky think about? To whom does he speak? Himself, it turns out: He kvetches about the disagreeable potential son-in-law he’s on his way to meet, broods over a friend’s comment that his latest book is repetitious, and complains about his constipation. But a novelist can’t help but look outward, and soon Parsky is not only creating a story about Marthe but wondering about this woman who can endure a long, sleepless train journey without, apparently, bringing a book. (One of Parsky’s novels is in her handbag, and she’s too timid to bring it out.) Reza’s story is encouraging to anyone who’s ever felt compelled to thank an artist for a book or song or painting: The Unexpected Man shows the route between observer and observed as a two-way street. Parsky may be a narcissistic grump, but he doesn’t exist in a vacuum: When he writes, he “throw[s] bottles into the sea, desperately hoping for a castaway.” He needs Marthe more than she needs him. Refreshingly free of neuroses, Marthe presides over a happy, normal life with only her Parsky-philia as an outsize feature; her zeal to talk to him is that of a courier with a life-changing message to impart. Largess and Giannarelli have shared the stage since the ’70s, and their rapport makes the tension of their characters’ growing curiosity about each other all the more captivating. Steven Carpenter moves them adroitly around Tracie Duncan’s set; they step from the upstage compartment down toward the audience, among valises and trunks, to unpack their own inner baggage. Marianne Meadows’ lighting and Daniel Schrader’s sound suggest the train voyage without overwhelming, but the story really comes down to those two wayfaring strangers—and the audience. When Parsky laments, “Is there one single person in the whole world who might know how to read this book?” you wriggle with delight at knowing the answer is right in front of him. —Pamela Murray Winters