“Hide quickly,” Kelson whispered, “those two are Hamar and Curtis.  Quick, for God’s sake—­or they will see you.”

Lilian Rosenberg hid behind an elm.

“Hulloa!” Kelson called out, advancing to the group.

“Why it’s you, Matt!” Curtis cried.  “Hamar said you would come!”

“Said I would come!  How the deuce did he know?” Kelson exclaimed.  “I didn’t know myself till the moment before I started.”

“I willed you,” Hamar explained; “as soon as I got back to my rooms after the Show, a voice said in my ears—­I heard it distinctly—­’Be at the Serpentine—­the south bank—­underneath a lime-tree—­you will know which—­at twelve to-night.’  I looked round—­there was no one there.  Naturally, concluding this was a message from the Unknown I hastened off to Curtis, who was in his digs—­and needless to say—­eating, and having dragged him away with me in a diabolical temper—­I then sought you.  Where were you?”

“Taking a walk.  I felt I needed it.”

“Alone!  Are you sure you weren’t out with some girl.”

“I swear it.”

“It seems as if I’m not the only liar!” Lilian Rosenberg said to herself in her place of concealment.  “What would Shiel say to that?”

“Humph!  I don’t know if I ought to believe you,” Hamar remarked.  “Did you feel me willing you to come here?”

“Rather!” Kelson said.  “That is why I came.  I seemed to hear your voice say ’To Hyde Park—­to Hyde Park—­the Serpentine—­the Serpentine.’” Then sinking his voice he whispered, “What’s up with the policeman, he looks deuced queer?”

“He’s in a trance.  We found him like this,” Hamar said.  “He is undoubtedly under the control of the Unknown.  I expect it to speak through him every moment.  Get ready to take down all he says.  I’ve come prepared,” and he handed Kelson and Curtis, each, a pencil and a reporter’s notebook.

He had hardly done so, when the policeman—­a burly man well over six feet in height, who was standing bolt upright as if at “attention,” his limbs absolutely rigid, his eyes wide open and expressionless—­began to speak in a soft, lisping voice that the trio at once identified with the voice of the Unknown—­the voice of the tree on that eventful night in San Francisco.

“The great secret of medicine—­the secret of healing—­will now be revealed to you,” the voice said.  “Pay heed.  In cases of tumours and ulcers take a young seringa, lay it for half an hour over the stomach of the afflicted person, then plant it with the mumia, i.e. either the hair, blood, or spittle of the sick person, at midnight.  As soon as the seringa begins to rot, the ulcer will heal.

“In phthisis pulmonalis, the mumia of the sick person should be planted with a cutting of the catalpa, after the latter has been subjected for some minutes to the breath of the diseased person.  As soon as the cutting shows signs of decay, the sick person will be cured.