s spines, it could not have been in
actual danger.

"How dost thou know of the tunneling?" I asked Aga. "Thy fish-men cannot
be present there, in the rear of the tunnel, to report."

"My artisans have knowledge of each forward move," she answered. "I will
show thee."

* * * * *

We walked back to the palace and descended to a smooth-lined vault.
There we saw a great stone shaft sunk down into the rock of the floor.
On this was a delicate vibration recording instrument of some sort, with
a needle that quivered rhythmically over several degrees of an arc.

"This tells of each move of the Quabos," said Aga. "It also tells us
where they will break through the city wall. How near to us are they,
Kilor?" she asked an attendant who was studying the dial, and who had
bowed respectfully to Aga and myself as we approached.

"They will break into the city in four rixas at the present rate of
advance, Your Majesty."

Four rixas! In a little over sixteen days, as we count time, the city of
Zyobor would be delivered into the hands--or, rather, tentacles--of the
slimy, starving demons that huddled in the cavern outside!

Somberly we followed Aga back to her apartment.

* * * * *

"As thou seest," she murmured, "there is nothing to be done. We can only
resign ourselves to the fate that nears us, and enjoy as much as may be
the few remaining rixas...."

She glanced at me.

The Professor's dry, cool voice cut across our wordless, engrossed
communion.

"I don't think we'll give up quite as easily as all that. We can at
least try to outwit our enemies. If it does nothing else for us, the
effort can serve to distract our minds."

He drew from his pocket a sheet of parchment and the stub of his last
remaining pencil. His fingers busied themselves apparently idly in the
tracing of geometric lines.

"Looking ahead to the exact details of our destruction," he mused
coolly, "we see that our most direct and ominous enemy is the sea
itself. When the city is flooded, we drown--and later the Quabos can
enter at will."

He drew a few more lines, and marked a cross at a point in the outer rim
of the diagram.

"What will happen? The Quabos force through the last shell of the city
wall. The water from their tunnel floods into Zyobor. But--and mark me
well--_only_ the water from the tunnel! The outer end, remember, is
blocked off in their pressure-reducing process. The v