Another of these odd slits in the rock was visible here, and the girl was able to perceive more clearly its nature--beyond question it was an artificial opening, leading into a space on the farther side of the wall.

Cateras pushed past her, his body interfering with her view, and bent down, fumbling along the rock surface.
"Hold the light closer," he demanded.

"Aye, that's it.

'Tis some trick to find the thing---- Ah! now I have it." It seemed like a bit of wood, so resembling the colour of the rock as to be practically imperceptible to the eye in that dim light--a bit of wood which slid back to reveal a heavy iron bolt, shot firmly into the stone.

This the Mexican forced back, and an opening yawned in the side wall, the rays of the lantern revealing the interior of a black cave.
Cateras stepped within.
"Bring the woman," he commanded shortly, "and you, Merodez, see first to the light." Silva thrust her forward, his grip no light one, while the other struck a match and applied it to the wick of a lamp occupying a bracket beside the doorway.