This spoof of the 1930s and '40s crime stories ranges from the ridiculous to the sublime as it tells the story of Johnny Dangerously (Byron Thames as the young Johnny, Michael Keaton as the older), a devoted son to his ailing mother (Maureen Stapleton), so ill that she needs money for several operations.
Johnny has nowhere to turn, and because gangsters tend to flourish in his neighborhood he goes to work for Dundee, a benevolent godfather-gangster type, in order to cover his mother's medical bills.
Johnny hides his association with Dundee from his younger brother Tommy (Griffin Dunne) and goes so far as to pay for Tommy's law school fees -- supporting him until Tommy joins the staff of the local (and corrupt) district attorney's office for Burr (Danny DeVito).
When Johnny starts working for Dundee, he clashes with the evil Vermin (Joe Piscopo) right from the beginning, but things only get worse. After Dundee decides to retire, Johnny ascends to the helm, and it does not look like Vermin is going to take that sitting down.