The Warlock's Grandfather (short story) (Warlock of Gramarye)

When old Count Rory, patriarch of d'Armand Automatons, begins to lose his grip on reality and retreat into a fantasy world, it threatens his company, his noble house, and his family. Is he just a senile but harmless old man, or a danger to himself and others? And what, if anything, can be done about it?