He was dead, and in death he lost his last and sole illusion.

He had sought a shelter in his son's heart, and it had proved to
be a sepulchre, a pit deeper than men dig for their dead. The
hair on his head had risen and stiffened with horror, his
agonized glance still spoke. He was a father rising in just anger
from his tomb, to demand vengeance at the throne of God.

"There! it is all over with the old man!" cried Don Juan.

He had been so interested in holding the mysterious phial to the
lamp, as a drinker holds up the wine-bottle at the end of a meal,
that he had not seen his father's eyes fade. The cowering poodle
looked from his master to the elixir, just as Don Juan himself
glanced again and again from his father to the flask. The
lamplight flickered. There was a deep silence; the viol was mute.
Juan Belvidero thought that he saw his father stir, and trembled.
The changeless gaze of those accusing eyes frightened him; he
closed them hastily, as he would have closed a loose shutter
swayed by the wind of an autumn night. He stood there motionless,
lost in a world of thought.

Suddenly the silence was broken by a shrill sound like the
creaking of a rusty spring. It startled Don Juan; he all but
dropped the phial. A sweat, colder than the blade of a dagger,
issued through every pore. It was only a piece of clockwork, a
wooden cock that sprang out and crowed three times, an ingenious
contrivance by which the learned of that epoch were wont to be
awakened at the appointed hour to begin the labors of the day.