"and now this sinister transformation in
Duror, itself an episode from a macabre
fairy-tale, suddenly in the wood the
straight stalwart immaculate ash tree
turning to a squat warty bush swarming
with worms."
Duror's state of mind declines rapidly
throughout the novel which results in
Lady Runcie-Campbell - who appears to
trust him a great deal - referring to him as
a "sinister transformation". He reaches
the point in which all the other characters
do not recognise him as someone they
knew.
All evil has taken over and it seems
that he is unable to control it.