A four-wheeler with an ancient nag between the shafts, clattered around a square. It drew up under a low arc light and took aboard a passenger who replaced his whistle in the pocket of his mackintosh.

“Two blasts,â€� explained Fay, “brings a deep-sea cab. One—a hansom!â€�

She glanced up at a corner lamp and said:

“Kentwater Road! I’m not going any further!�

“Why?�

She turned and stared toward the east. “Do you remember Sir Richard saying ‘Come here, Mac, come here?’�

“Yes, I do.�

“What did he mean by that? Why didn’t Mr. MacKeenon follow us? He could.�

Fay hesitated. He went back over the scene in the great room where Saidee Isaacs had switched off the lights. “Yes, he could,� he admitted finally. “I wonder why he didn’t?�

Her hand grasped his overcoat sleeve. “I believe they found the cipher-key! Don’t you see—they must have found it!â€�