That both of these women are portrayed by Laura Linney is the neat trick of Lucy Barton. In an enthralling performance, Linney embodies both memoirist and memory. Did Lucy's mother even show up, or was she a hospital fever dream? She certainly sounds authentic, and has a real effect on Lucy when she jostles the worst of her daughter's past to the surface. The play, a 90-minute one-act, is a monster of a monologue: Realistic in reflecting the ways that recollections can be inconsistent and tangential, but all the more difficult to memorize for being so. Linney's delivery is seamless. (The show's sound cues, intrusive here, suggest music wafting in from another patient's room; neither the actor nor the audience need them.)