at the fiddle

Engaged in deceitful, fraudulent, or dishonest means of obtaining money. My career will be over if anyone ever finds out I was at the fiddle during my time as the company treasurer. There are always politicians at the fiddle, looking for ways to use their positions of power to increase their wealth. A: "I can't believe that Margaret was actually at the fiddle this whole time." B: "I know! She's the last person I would have suspected of stealing money."