More than four years after the financial crisis, not one senior Wall Street executive has faced criminal prosecution for fraud.

Are Wall Street bankers simply “too big to jail?”

In The Untouchables, FRONTLINE producer and correspondent Martin Smith investigates why the U.S. Department of Justice has failed to act on credible evidence that Wall Street knowingly packaged and sold toxic mortgage loans to investors, loans that brought the U.S. and world economies to the brink of collapse.

So, after talking with top prosecutors, government officials and industry whistleblowers, what did he find? Is there a chance some prosecutions may still take place? What do we really know about the criminal cases that could be have been pursued? And what does this investigation reveal about Wall Street and its relationship with the government?

We’ve invited producer Martin Smith and New York Times DealBook reporter Peter Eavis to join us to discuss these questions and take yours.

You can leave a question in the chat window below, and come by on Wednesday at 2pm. ET to join the live discussion.