As the show opens, a Bajoran transport carrying Kai Winn and Vedek Bareil suffers a mishap, and Bareil is left injured. He is brought on board Deep Space Nine, where he is treated by Dr. Bashir. They soon, however, find that he is braindead. Because Bareil was in the midst of negotiations with the Cardassians, the talks would collapse without him, so Bashir suggests a radical procedure - replacing the damaged part of his brain with a positronic matrix.
The surgery is a success, except for the fact that Bareil is still severely brain-damaged and can live only for several months, just enough time to hopefully conclude his negotiations with the Cardassians. His lover, Major Kira, speaks with him, but he barely recognizes her. He is no longer the man she fell in love with.
Bareil is kept alive long enough to aid in completing the negotiations, and the treaty is formed between Bajor and Cardassia. As Bareil's condition worsens, Kira insists Bashir replace the remainder of his damaged brain with positronic matrices, but Bashir refuses on the grounds it will remove any 'spark of life' Bareil has left. The episode closes with Kira sat at the bedside, regaling a slowly dying Bareil with the tale of how she first fell in love with him.