Mary Stewart: The Gabriel Hounds [1991] paperback

When the Gabriel Hounds run howling over the crumbling palace of Dar Ibrahim in the Lebanon, someone will shortly die. An eccentric old Englishwoman, 'Lady Harriet', lives there in decaying splendour and complete seclusion. The isolation is broken by the arrival of rich young Christy Mansel and her cousin Charles. All too soon they discover that if entrance to the palace is difficult, retreat from it is almost impossible - and the legend of the Gabriel Hounds becomes frighteningly real.