Neil LaBute’s new play for MCC at the Lucille Lortel Theatre is really just an hour-long monologue for an actress on the far side of 50. But when that actress is Tony winner Judith Light, who’s going to complain about it? Light plays Mrs. Johnson, a long-time high school English teacher and counselor, looking back 15 years to a relationship that profoundly affected her marriage, her career and her soul. To say more would be to give away too much. Those expecting the usual dose of bile and surprise from LaBute will be disappointed. Light is impressive — just learning all those lines is amazing — but her performance is too often overheated with few quieter moments to relieve the intensity. Rachel Hauck’s set recreates a high school office convincingly. Emily Rebholz’s has dressed Light plausibly. I wish director Leigh Silverman had gone for a wider emotional palette. Running time: one hour, no intermissionion.