User blog comment:AgnesFlether/"The kindness of strangers" episode review/@comment-5086871-20121208232922/@comment-5674726-20121209015950

Aithusa betrayed him!

Aithusa is staying with the the woman who endured two years of imprisonment and torture rather than risk her by using magic to escape, and who has tried to care for her since their escape.

If Kilgharrah is dying then killing Aithusa would mean wiping out their kind.