“The evening post, sir,” he said, handing the salver to Ackroyd.

 

Then he collected the coffee cups and withdrew.

 

My attention, diverted for a moment, came back to Ackroyd. He was staring like a

man turned to stone at a long blue envelope. The other letters he had let drop

to the ground.

 

“_Her writing_,” he said in a whisper. “She must have gone out and posted it

last night, just before—before——”

 

He ripped open the envelope and drew out a thick enclosure. Then he looked up

sharply.

 

“You’re sure you shut the window?” he said.

 

“Quite sure,” I said, surprised. “Why?”

 

“All this evening I’ve had a queer feeling of being watched, spied upon. What’s

that——?”

 

He turned sharply. So did I. We both had the impression of hearing the latch of

the door give ever so slightly. I went across to it and opened it. There was no

one there.