A walker in the woods spots a dead ash tree he has somehow never noticed before. The sun lights it up, and the gap where its life used to be now lets the light in. The speaker admits that for years he read the tree as an eye, as though the woods had been watching him all along, and only now does he see it properly.
The poem then widens. A small island in the stream, and the mounds where roots once held the earth, lead him to a quiet warning: don't call them "Indian graves." The speaker seems to be correcting a careless assumption, whether his own or a local habit of speech. The ending is humble. Whether you believe in God or in microbes, he says, there is always something undiscovered around us. The mood is hushed and curious, tinged with loss but mostly with wonder at how much we overlook, even in places we think we know.