l be a race against time."

"Natalie will not come."

"Not voluntarily. You must think of some plan. Your brain is quick. We
have not a moment to lose. Ah, there she is! Speak to her."

Natalie was crossing the open ground which led from the glen to Brande's
laboratory. She did not observe us till Edith called to her. Then she
approached hastily and embraced her friend with visible emotion. Even to
me she offered her cheek without reserve.

"Natalie," I said quickly, "there are three horses saddled and waiting
in the palm grove. The _Esmeralda_ is still lying in the harbour where
we landed. You will come with us. Indeed, you have no choice. You must
come if I have to carry you to your horse and tie you to the saddle. You
will not force me to put that indignity upon you. To the horses, then!
Come!"

For answer she called her brother loudly by his name. Brande immediately
appeared at the door of his laboratory, and when he perceived from whom
the call had come he joined us.

"Herbert," said Natalie, "our friend is deserting us. He must still
cling to the thought that your purpose may fail, and he expects to
escape on horseback from the fate of the earth. Reason with him yet a
little further."

"There is no time to reason," I interrupted. "The horses are ready. This
girl (pointing as I spoke to Edith Metford) takes one, I another, and
you the third--whether your brother agrees or not."

"Surely you have not lost your reason? Have you forgotten the drop of
water in the English Channel?" Brande said quietly.

"Brande," I answered, "the sooner you induce your sister to come with me
the better; and the sooner you induce these maniac friends of yours to
clear out the better, for your enterprise will fail."

"It is as certain as the law of gravitation. With my own hand I mixed
the ingredients according to the formula."

"And," said I, "with my own hand I altered your formula."

Had Brande's heart stopped beating, his face could not have become more
distorted and livid. He moved close to me, and, glaring into my eyes,
hissed out:

"You altered my formula?"

"I did," I answered recklessly. "I multiplied your figures by ten where
they struck me as insufficient."

"When?"

I strode closer still to him and looked him straight in the eyes while I
spoke.

"That night in the Red Sea, when Edith Metford, by accident, mixed
morphia in your medicine. The night I injected a subtle poison, which I
picked up in India on