But now there came a dull muffled explosion--the strange bomb. Instantly
the men below began acting like madmen. Throwing away their rifles, they
staggered about, tearing at their eyes, their throats, their clothing,
and uttering wild cries of distress. At the same time three automatic
pistols cracked, and Dave knew the doctor had given his signal.

To his surprise, he saw the three jackies emerge from hiding wearing gas
masks. Quickly they overpowered the wild men, tied them and carried them
around a point of land. As they did this the Doctor and his band kept
guard above, rifles ready for any man who might, by some chance, recover
sufficiently from the gas to shoot. But none did.

"It won't do them the least bit of harm," the Doctor said, as he noticed
the look of surprise on Dave's face. "It's only chlorpicrin--a tear gas.
It comes in liquid form, so must be associated with an explosive which
transforms it into a gas and scatters it. You will see that our men are
carrying them out of it as soon as they have them secured. It's a safe
and harmless way of handling criminals. The war taught us that."

"But the ensign?" exclaimed Dave, as he saw the last ruffian in the hands
of the jackies.

"Something must have happened to him," said the Doctor rising hastily.

"There was a shot," Dave reminded him.

Together they hastily made their way down the rough hillside. Slipping,
sliding, falling, to rise again, they came to the lower surface and
hurried around the point where the prisoners had been carried.