Manslaughter by Alice Duer Miller

Before the lights went up on the first entr'acte Lydia retreated to the little red-lined box of an anteroom and sank down on the red-silk sofa. She and Miss Bennett had come alone to the opera; but Dorset and Albee, who was committed to some sort of political dinner first, were to join them presently.

Even while the house was still in darkness Lydia had recognized the outline of O'Bannon's head in a box across the house. She had seen it before she had seen Eleanor. Miss Bennett had stayed in the front of the box. Lydia was glad she had. She wanted to be alone while she waited. She could see her between the curtains, sweeping the house with her opera glasses.