Possible Clues:

• Corrupts
• Traces of discredit
• Introduces impurities to
• What spoils this is not what's in up the street
• It is not what is in there up the street that spoils the taste of it
• Stains
• It is not what's in the backstreet that spoils it
• It is not in the backstreet that this pollutes things
• Such badness is not in the backstreet
• What's not in there up the street is what spoils it