gallops away and leaves the knight alone.

Gawayne now pursues his journey, rides through the dale, and looks
about. He sees no signs of a resting-place, but only high and steep
banks, and the very shadows of the high woods seemed wild and
distorted. No chapel, however, could he discover. After a while he sees
a round hill by the side of a stream; thither he goes, alights, and
fastens his horse to the branch of a tree. He walks about the hill,
debating with himself what it might be. It had a hole in the one end
and on each side, and everywhere overgrown with grass, but whether it
was only an old cave or a crevice of an old crag he could not tell (ll.
2149-2188).

"Now, indeed," quoth Gawayne, "a desert is here; this oratory is ugly
with herbs overgrown. It is a fitting place for the man in green to
'deal here his devotions after the devil's manner.' Now I feel it is
the fiend (the devil) in my five wits that has covenanted with me that
he may destroy me. This is a chapel of misfortune--evil betide it! It
is the most cursed kirk that ever I came in." With his helmet on his
head, and spear in his hand, he roams up to the rock, and then he hears
from that high hill beyond the brook a wondrous wild noise. Lo! it
clattered in the cliff as if one upon a grindstone were grinding a
scythe. It whirred like the water at a mill, and rushed and re-echoed,
terrible to hear. "Though my life I forgo," says Gawayne, "no noise
shall cause me to fear."

Then he cried aloud, "Who dwells in this place, discourse with me to
hold? For now is good Gawayne going right here if any brave wight will
hie him hither, either now or never" (ll. 2189-2216).