But the entrance to them was by a narrow shaft which rose sharply from a cave in the heart of the knoll.

On this shaft the Twins had spent their best pains for two and a half wet days the year before; and they had reduced some seven or eight feet of it to a passage fifteen inches high and eighteen inches broad.

The opening into this passage could, naturally, be closed very easily; and then, in the dim light, it was hard indeed to distinguish it from the wall of the cave.

It had been a somewhat difficult task to get their blankets and provisions through so narrow a passage; but it had been finished soon after breakfast.
They were on the alert for invaders; and as soon as they were quite sure that the keen ears of Erebus had made no mistake and that a car was coming up the board aisle, the princess and the Terror squirmed their way up to the secret caves; and Erebus closed the passage behind them, and with small chunks filled in the interstices between the larger pieces of stone so that it looked more than ever a part of the wall of the cave.

Then she betook herself to a point of vantage among the bushes on the face of the knoll, from which she could watch the entrance of the path and the coming of the invaders.
The archduke, lying back at his ease in the car, and smoking an excellent cigar, spoke with assurance of catching the one-fifteen train from Rowington to London and the night boat from Dover to Calais.