Related Clues:

• State of high alarm
• Pre-meltdown signal, maybe
• Danger signal
• 'The enemy is upon us!'
• Period of crisis
• Serious warning
• Warning signal
• Danger sign
• Warning to heed
• Signal of imminent danger
• Emergency on the Enterprise
• Pre-attack state
• Imminent-danger warning
• Emergency state
• Imminent danger warning