Possible Clues:

• Having moved slowly, I have to drop sharply
• (Make a) steep downward plunge
• Sudden and dramatic deterioration
• Steep downward plunge by aircraft
• Even so, I'd resolved to take the plunge
• Swiftly drop nameless salad plant boy originally picked up
• I have investigated first sudden decline
• Go carefully - rich man shortly going to fall precipitately
• Front-first fall
• Sudden drop