Possible Clues:

• Soothsayer's sightings
• Threats from very big blokes inside!
• Calpurnia's dream in 'Julius Caesar' and others
• Oracle's signs
• Signals of what's to come
• Signs that may bring bad luck
• Old chaps beginning to see warning signs
• Spilled salt and gathering clouds, to some
• Shooting stars, to some
• Foretelling signs