The 'walk' in 'ghosts walk' doesn't refer particularly to perambulation as such. If a ghost is [felt to be] active, it 'walks'.
That said, I agree that the last sentence in that extract 'comes out of left field'. Perhaps the dead people referred to are Mrs Schiller and her stillborn child. Alternatively it would be quite difficult to write a biography without people dying in it. But I am really flummoxed...
Interested in Language