“The man I saw in the jewelry store!” gasped Grafton.  “I remember, now, seeing you there the day I went to look for the diamond cross.”

“And didn’t find it,” said the detective.  “I wondered what so perturbed you, but now I know.  At first I did think you might know something of the murder—­”

“God forbid!” said the merchant earnestly and reverently.

“Amen!” echoed the colonel.  “You have told such a straightforward story that I can not doubt you.  That is why I revealed myself to you.  But you must keep my secret if I am to help you.  I am known in Colchester as Colonel Brentnall, having registered at the hotel under that name.  I will keep that name for the present.  I followed you here—­in fact, I only entered this office a minute or two ahead of you.  So it was to find the diamond cross you visited the store of the murdered woman?”

“Yes.  When I had damaged the cross by stepping on it, I thought my old friend, Mrs. Darcy, would be the best one to keep my secret.  I took the cross to her the night before she was killed, and she promised to have her cousin fix it without telling him whose it was and get it back to me, secretly, in a day or so.

“I thought Cynthia could then wear it again without her husband knowing it had ever been out of her possession.  But the murder changed all my plans.  As soon as I could, I went to the shop to look for the cross.  I thought perhaps it might have been put in one of the showcases, or laid on the shelf, perhaps forgotten.  Really I was so distressed, I didn’t know what to think.  I did not want to tell any one what I was looking for, so I went about quietly.  But I could not find it.  Then I was obliged to ask Darcy about it, secretly, of course, and without hinting as to the ownership.

“But he had never seen it.  He said Mrs. Darcy had not given it to him, nor asked him to repair it.  Nor was it in the shop, as far as he knew, and he went over all the stock to furnish a list to the police, so they could tell whether or not there had been a robbery.”

“And there was none?”

“None, unless you call the taking of the diamond cross a theft.  For that alone is missing.  And I’d give half my fortune to get it back.  Cynthia’s husband may ask about it at any moment, and what excuse can she give?”

“It is rather a ticklish matter,” agreed the detective.  “Well, I’ll see what I can do.  First I thought you wanted me to work on the murder case.  But as I am already engaged on that, to try to clear Darcy, I can as well include the diamond cross mystery also.  I wonder if they have any connection.”

“I don’t see how they can have.  Mrs. Darcy may merely have put the cross away secretly, and it may take a careful search of the place to find it.”

“Maybe so.  I’ll have to nose around a bit.”

There came a knock on the office door.

“Come!” called out the colonel.