for steven o'donnell, growing up in a blue collar neighborhood in providence, rhode island, organized crime was a fact of life and he was top dog. >> i was fascinated with organized crime. >> reporter: fascinated but determined to stay on the right side of the law. he started as a maximum security prison guard learning the language of the mobsters. >> without question the work in the prison set me up for some type of success. >> reporter: on one faithful day in 1994 on the steps of the providence courthouse, o'donnell, now an undercover cop, found himself face to face with a mob hit man out on parole. >> you seized the moment. >> i saw him and hi to get rid of the warrants and talk to him. convincing him they had done time together. >> he bought everything? >> ic convinced him i was a inmate. >> reporter: so began the big lie. he was steve foley now. living someone else's life. he was all in. >> i was a book maker. i was a drug dealer. they thought i was buying large amounts of cocaine and heroin and pot, marijuana. >> reporter: six years in the shadows moving with mobsters building a

for steven o'donnell, growing up in a blue-collar neighborhood in providence, rhode island, organized crime was a fact of life, and the patriarch of mob family was top dog. >> i was fascinated with organized crime. >> reporter: fascinated but determined to stay on the right side of the law. o'donnell started off as a maximum security prison guard, learning the language of the mobsters. >> without question, we work in the prison set me up for some type of success, because i could walk the walk, talk the talk. >> reporter: on one fateful day in 1994, on the steps of the providence courthouse, o'donnell, now an undercover cop, found himself face to face with harold tillinggast, a mob hit man out on parole. you seized the moment. >> i was coming to get a warrant signed unrelated. i saw him and i had to get rid of the warrants i had and then just talked to him. >> reporter: talked not like a cop but like a guy from the hood, convincing tillinggast they had done time together. he just bought everything, hook, line and sinker? >> i convinced him i was an inmate. i knew what the cell block me