Joanne asked no questions.
Her lips were set tight.

She was pale.
At the end of three quarters of an hour it seemed to them that MacDonald was riding directly into the face of a wall of rock.

Then he swung sharply to the left, and disappeared.

When they came to the point where he had turned they found that he had entered a concealed break in the mountain--a chasm with walls that rose almost perpendicular for a thousand feet above their heads.

A dark and solemn gloom pervaded this chasm, and Aldous drew nearer to MacDonald, his rifle held in readiness, and his bridle-rein fastened to his saddle-horn.