“What I think,” he said, driving with the one-handed casualness which sets my teeth on edge, “is that she saw something. She may have looked through a window and seen Mrs. Wainwright kill herself; or more likely she saw someone else there. What we can’t make out is why she was there herself, at that hour. When we left she was reading a book and going to bed early. Bill Sterling was out on a case.”

Fifteen minutes later I pushed open the door to Lydia’s room and walked in. She was not in bed. She was partially dressed, and was looking out toward the river. When she turned and saw me she had to catch a chair to steady herself.

“Pat!” she said. “You scared me.”

I took one look at her and put her into a chair. Then I kissed her, and she drew a long breath.

“I thought it was the police,” she said, and closed her eyes.

I gave her a little time to recover, talking of other things. Her color came back, but she was still a wreck of her former self. Her eyes were sunk in her head, and the life had gone out of them. Also I saw she was suspicious of me. She dodged every attempt to bring in the Cloisters, and at last I simply sat forward and said, “Why don’t you tell me all about it, Lydia?”

I had expected more evasion, but it did not come. Instead she made a small gesture of surrender.

“I’ll have to tell somebody. If I’m arrested it will finish Audrey. And poor Bill—”

“You’ll not be arrested, Lydia. It need never come out at all. You were there that night. I happen to know it. Do you want to tell me why?”

“You won’t believe it.”

“I don’t see why not, Lydia. I’ve believed you for a good many years.”

“All right. I was there because she sent for me.”

“Sent for you!”

“That’s what she did. At first I was to go to the house. Then, about seven o’clock that night, she called again. She said Bessie was having some people to dinner, and did I object to going to the playhouse instead.”

She hadn’t wanted to go there. She couldn’t bear to think of the place. She asked Maud to come down to her house instead. But Maud said what she had to say was private. If she went someone would have to take her, and she didn’t want it talked about.

“I hate to ask you,” Maud said, “but I assure you it is important. It won’t be bad, Mrs. Morgan. I’ll light a fire in the living room. We can be alone, and nobody needs to know anything about it.”

The time, to her surprise, was to be eleven-thirty, and Lydia had demurred somewhat. But Maud had been firm. She could get rid of the maid by that time, and the matter was extremely confidential.

“She said something about Audrey,” Lydia said. “I thought she must mean Tony and Audrey, although that was over months ago. But it all seemed strange enough. Then I began to worry about Bill. Perhaps she knew something that would bring him back into Don’s murder or connect him with Evans. You know how it is. You build up all sorts of things.”