I meant to type Ricca, but ended up thinking of Giancana while also mentioning Accardo. I not too sure Campagna would've been involved in a plot like that, he was supposedly pretty loyal to Capone. And Curly Humphrey's was well on his way up prior to Capone even being indicted. Humphrey's was the working force behind a lot of Capone's business takeovers. I don't think anyone was necessarily trying to get rid of Capone, or that one of his guys were feeding the tax guys info. I'm not sure they ever did. This was covered in "The Outfit" as well. Capone's tax indictment was literally something of happenstance somewhat. A bookmaking and gambling den that he controlled was raided at one point. I forget which law enforcement agency it was, but they basically found a book which had listed Capone's gambling assets, and the money he was making from the alcohol and other things. Nobody initially thought anything of it, and it was kept locked in a file cabinet for some years. While investigating Capone, that book was one of the things that was looked into, and they saw that his earnings for that time period didn't match what he was putting into his taxes. One thing led to another and he was indicted. However, after Capone was put away, guys did little to help him out on an appeal, which supposedly could've been a real option.