From fall to spring, J.A. Baker set out to track the daily comings and goings of a pair of peregrine falcons across the flat fen lands of eastern England. He followed the birds obsessively, observing them in the air and on the ground, in pursuit of their prey, making a kill, eating, and at rest, activities he describes with an extraordinary fusion of precision and poetry. And as he continued his mysterious private quest, his sense of human self slowly dissolved, to be replaced with the alien and implacable consciousness of a hawk.

It is this extraordinary metamorphosis, magical and...