You are in the finishing stages of an audit of a large publically held for-profit education company currently under investigation by the government for its recruiting and gainful employment reporting practices. Prior to the completion of your audit, the CFO steps down and accepts a buyout and severance worth several million dollars. When you complete the audit shortly thereafter, the former CFO refuses to sign the representation letter or discuss anything regarding his former employer. His replacement was brought in from outside the company and has little knowledge of the day-to-day affairs prior to his arrival.

How would you handle this situation? What alternatives are available to you?

Withdrawing from the engagement is a last resort and highly unlikely.  

Spend little to no time discussing that option.  Focus your discussion on other alternatives.