The Expensive Halo by Josephine Tey — Read

Sara let herself in with her mother's latch-key. She had shown her mother Ursula's invitation, and begged for her co-operation. She would have liked to tell her mother the whole truth; all about Chit, everything. But she knew that the mention of Chit would excite her mother's alarm and produce a lecture about keeping her place, and no latch-key. So she let it be understood that Ursula was inviting her because she had seen her so often in the shop and wanted to give her some pleasure. Mary Ellis was touched that someone who was almost a stranger should have cared for her daughter sufficiently to invite her to her party, and sympathised with Sara's eagerness to go, but she was no fool. She handled the invitation thoughtfully, and said: "You're telling me the truth about this, Sara?"

Sara had said: "Certainly," and thought: "It's your own fault if I've left something out." But she had been grateful and a little moved by her mother's willingness in planning the evasions which were to make the party possible for her. Her father was to be left under the impression that she was in bed; she often went early to bed, where she could read in peace; and there would be no overt lies on her mother's part. At ten o'clock she would say as usual: "Will you turn the latch in the door, Father?" And the latch would be turned by her unsuspecting parent and opened by Sara with her mother's latch-key when she came home.