"On your own head be it," said Homo, his hard face creased in a fleeting smile.
Beale's car was waiting, but his departure was unexpectedly decayed. As he passed down the stairs into the vestibule he saw a stranger standing near the door reading the enamelled name-plates affixed to the wall. Something in his appearance arrested Beale. The man was well dressed in the sense that his clothes were new and well cut, but the pattern of the cloth, no less than the startling yellowness of the boots and that unmistakable sign-manual of the foreigner, the shape and colour of the cravat, stamped him as being neither American nor British.
"Can I be of any assistance?" asked Beale. "Are you looking for somebody?"
The visitor turned a pink face to him.
"You are very good," he said with the faint trace of an accent. "I understand that Doctor van Heerden lives here?"
"Yes, he lives here," said Beale, "but I am afraid he is not at home."
He thought it might be a patient or a summons to a patient.
"Not at home?" The man's face fell. "But how unfortunate! Could you tell me where I can find him, my business is immediate and I have come a long way."
From Germany, guessed Beale. The mail train was due at Charing Cross half an hour before.
"I am a friend of Doctor van Heerden and possibly I can assist you. Is the business very important? Does it concern," he hesitated, "the Green Rust?"
He spoke the last sentence in German and the man started and looked at him with mingled suspicion and uncertainty.
"It is a matter of the greatest importance," he repeated, "it is of vital importance."
He spoke in German.
"About the Green Rust?" asked Beale, in the same language.
"I do not know anything of the Green Rust," said the man hurriedly. "I am merely the bearer of a communica-
