Very quietly...

so as not to disturb the thing that sleeps, you push away the tall grass along the back of the milestone in order to get a better look at the inscription. The moonshine lends the unweathered back of the milestone a glow as if from a halo and the deep-cut letters you find shine in full relief. The cast shadows of each letter's edge fall deep into the carving, making them appear as sharp as on a printed page.

In other words, you have no trouble reading the inscription and it says:

"The first thing you must do is forgive your parents for ever bringing you into this world."

The thing that sleeps in the bushes sharply snorts, as if on cue, abruptly bringing you back to your senses.

Do you:
-inspect the sound behind the bushes

Or do you:
-walk to the plane
-look in the crack in the earth
-Run away down the road