go off the
Hell-Hole Isthmus," he said.

The two strangers drew closer and listened intently to the news while
Dickie chafed at Gregory's failure to get under way.

"That means we've got to be off," exclaimed one of the men. "How about
going over in that speed-boat of yours?"

Gregory nodded. "That's what I was figuring on," he said. "I'm going to
send a radio to all my boats within a thirty-mile radius of the island
to reinforce the fleet and mix it with Mascola off the Hell-Hole Isthmus
on the north side. While they're busy on that side, it will leave us a
clear field on the other."

Dickie's eyes opened wide at his words. As they moved away together in
the direction of the cannery, she cried: "I don't understand at all.
Aren't you going to help the boys out?"

Gregory shook his head and the grim lines tightened about his mouth.

"No," he answered. "Not this time. That is what Rock, Bandrist and
Mascola think I am going to do. But I'm going to fool them. There's
something back of all this that we can only guess at now. Diablo has a
secret our fathers died to learn. I'm sure of it now. To-night I'm going
to find out what it is."

CHAPTER XXVIII

THE ISLAND'S PRISONER

Diablo was steeped in moonlight. For miles about the sea gleamed like a
mirror. The grim mountains which guarded the shore were robed in saffron
and checkered with black by the dark shadows of the towering peaks as
they fell athwart the hillsides and mingled with the darkness which
hugged the canyons.

From a small cave high up on a rocky canyon wall the figure of a man
emerged and crept silently into the shadows. Picking his way with great
caution along a winding sheep-trail, he reached the summit of the hill
and looked about. The damp sea air fanned his long hair and caused him
to look in the direction of the fleecy white clouds which were creeping
upward from the horizon. Soon there would be fog. Then he could continue
on his way to the brackish spring on the bluff-side overlooking the
south shore. From there it was only a stone's throw to the beach where
the mussels and abalones clung so thickly to the rocks.

The thought of the raw shellfish sickened him. For days he had had
nothing else to eat. Shrinking closer into the shadows of the sage and
cactus, he waited for the fog. Then he could go on on his nightly
journey. How many months had he been a prisoner on El Diablo? He had
lost all track of time. But what did it matter? Soon