The narrator of “Stairs” is one Tassie Keltjin, who is looking back on her 20th year. Having grown up on a small Midwestern farm, Tassie has never taken a taxi or an airplane, never eaten Chinese food, never seen a man wear jeans with a tie. Though her brother, Robert, who is desultorily thinking of joining the military, looks up to her as a focused, sure-footed college girl, she thinks of herself as lost, as lacking the ambitions of friends (“marriage, children, law school”) and lacking an internal gyroscope that might lend ballast to her plans.