WMAQ-TV's investigative team studies the pleas of innocence from four men who were convicted of gang rape and murder in the late 1970's. For 18 years, the four had plead their innocence to police, prosecutors, judges and juries. In trial after retrial, they'd been found guilty. With the aid of a Northwestern University professor and three of his students, WMAQ found an 18-year-old police report, long buried, that both pointed to the four's innocence and targeted the real killers. The investigation also revealed an audio tape confession of the actual triggerman.