therein lies the rub

• there lies the rub
• there is the rub

A misquotation or paraphrasing from Shakespeare's Hamlet: "ay, there's the rub".

therein lies the rub

1. That is where the problem is found or located.

   I tried to back up my database to a USB flash drive, but it isn't big enough. Therein lies the rub.

• thereby hangs a tale
• where the shoe pinches

• “there s here s the rub” in Longman Dictionary of Contemporary English, Longman.
• “therein lies the rub”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.
• “theres the rub”, in Collins English Dictionary.