Possible Clues:

• Stunning surprise
• Upset of the century, say
• Terrible performance in football, as drunk might be heard to say
• It's a nasty thing -- that's half of what we hear from the preacher about wine
• Major upset, say
• The shower scene in 'Psycho,' e.g
• Something unsettlingly surprising
• Surprising revelation
• Bombshell
• Cheap thrill - traditionally a good bob's worth