Despite some good performances, especially out of Dan O'Herlihy as a gentleman bank robber, this episode of The Untouchables was far from accurate as to how bank robbery became a federal crime.
When the Federal Deposit Insurance Corporation was formed to insure that banks would not be subject to the boom and bust cycle, those banks who joined it came under federal jurisdiction. If you remember the classic Don Siegel film Charley Varrick Walter Matthau and his gang targeted a specific small southwestern bank because it did not carry insurance and hence it would not be a federal crime. Treasury agents were not involved in this area of law enforcement at all. Bank robbery became the jurisdiction of J. Edgar Hoover and his agency. That's who Federal Attorney Frank Wilcox would have called on to gather evidence to make bank robbery a crime, not Eliot Ness.
Still Wilcox does call on Robert Stack and his team and investigate they do. O'Herlihy is one smooth operator and he doesn't make mistakes. And to take care of mistakes he has James Mageean as his enforcer.
Mageean also stands out in this story. His brogue is unmistakable and although it's never brought up he probably learned his trade in the old country fighting in the Rebellion and later the Irish Civil War.
Untouchable episodes take a lot of liberties, but this one was too much.