"The Call throws the Ordinary World off balance, and establishes the stakes involved if the challenge is rejected.
The Call to Adventure can take a multitude of forms, including: a message or announcement a sudden storm, the arrival of the villain, a death, an abduction, a man’s dying words... The Hero may need a Succession of Calls before finally realizing that a challenge must be met, or that his only means of escape is the Special World. Many times the Hero needs to choose between two Conflicting Calls..."
-Christopher Vogler