Possible Clues:

• Cops the mysterious type concealed by monitor
• Cops the elite type of underground flower pests
• A mysterious force?
• Undercover lawmen
• Undercover cops - elite crew perhaps - no women!
• They are not openly in force
• There's no telling how they enforce the law
• Guards on the Underground?
• Cops, elite crew endlessly trained for special force
• Those shadowy sorts? They probably keep the blue flu to themselves