It was midnight before she made any move. The household was asleep. Even Amos’s light in the stable was out, by that time. But she took the precaution of slipping off her shoes. Then, armed with her flashlight, she went up to the third floor. She did not go back to Ida’s room, however. She went into the guest rooms, taking one after the other, examining the floors and the bathrooms, and removing the dust covers from the beds.

It was in the room over Carlton’s that she found what she had been afraid to find.

She went to bed and to sleep after that, but she carried a sort of mental alarm clock in her head, and promptly at six she wakened. Nobody was stirring in the house when she went down to the library and called the inspector on the phone at his bachelor apartment. His voice was heavy with sleep when he answered.

“It’s Hilda Adams,” she said carefully. “I want you to do something. Now, if you will.”

“At this hour? Good heavens, Hilda, don’t you ever go to bed?”

“I do, but I get out of it. Will you have someone check the hotels in town for a woman who got there early Sunday morning and left that afternoon?”

“Sunday? Sure. But what’s it all about?”

“I’ll tell you later. I can’t talk here.”

She hung up and went upstairs again. She had been stupid, she thought. She should have known all this before. Yet she had also a sense of horror. It was still written all over her when she sat in the inspector’s office that Wednesday morning.

“How did you guess it?” he said.

“Then it’s correct?”

“Correct as hell. She checked in at five Sunday morning and left that afternoon. She left Atlantic City on Saturday.”

She drew a long breath.

“I should have known it before,” she said. “The figure at the top of the stairs and the chandelier shaking. I think young Brooke saw it, too, although he denies it. But the rooms looked the same. Only Ida had cleaned a bathroom, and she couldn’t put back the dust. I suppose that cost her her life. If she had only raised a window and let the dirt in—”

In spite of himself Fuller smiled.

“The world lost a great criminal in you, Hilda,” he said admiringly.

He looked over his notes. Marian had registered at one of the big Atlantic City hotels the night she had left home. She had remained most of the time in her room, having her meals served there, and she had left on a late train on Saturday.

“It checks,” he said thoughtfully. “She came home late and Ida probably admitted her and told her Eileen was there. She smuggled her up the back stairs to the third floor and settled her there. Then what? Did she come down while young Brooke was with Jan, and stab her mother? It’s—well, it’s unnatural, to say the least.”