cried, "a permit from Rao Khan, admitting me to the prison at
all times. I told him that your wound was very bad, that the Arab doctor
had failed to help you, and that I knew enough of English surgery to
cure you if he would allow it. Rao Khan reluctantly consented, and here
I am."

He listened intently for a moment, glanced round the dungeon, and then
went on in a low, excited tone:

"Get close together. I have something important to tell you."

They squatted down in a group on the straw, and with a strange, exultant
sparkle in his eyes, Canaris began:

"When I came to Harar two years ago this very cell held a white slave,
like yourselves an Englishman. He was an old man, with long white hair
and beard, and had been so long in slavery that he had forgotten his own
name and could scarcely speak the English tongue.

"My duties then were to carry food and drink to the slaves, and before
long I was on intimate terms with the old Englishman. He was very ill,
and the Arab doctors made him no better. Perhaps it was old age that was
the trouble, but at all events he died two months after I came. At
different times he had told me the story of his life, and that is what I
am going to tell you now.

"He had been thirty years in slavery. How and where he had been captured
he could no longer remember. His mind was a blank on that point. But one
thing he told me that is important. For twenty years he had lived among
the Gallas in a village fifty miles to the south of Harar, and it was a
few years after he had been brought there that he nearly succeeded in
making his escape.

"He had often heard from the natives of an underground river that was
said to exist, and which emptied either into the River Juba or into the
sea. The tales concerning the river were many and strange, but the chief
of the Gallas assured him that at one time a tribe of natives had lived
in the mouth of a huge cavern which gave access to the river."

"I have heard something of that myself," interrupted Melton. "An Arab at
Zanzibar told me, but I never had any faith in the story."

"That river exists," said Canaris solemnly. "The Englishman found it."

"What!" cried Guy and Melton in one breath. "He found the underground
river?"

"Yes, he discovered it," resumed Canaris. "He found it one day while
hunting in a concealed cavern. He ventured down and came to a great
sandy beach, past which flowed swiftly a broad stream. On the beach lay
half a dozen stro