A man named Ritchie (Morgan Sha'an) is stabbed during a prison power play. In the infirmary, he admits to an orderly that he was the one who murdered the man the orderly was convicted of killing. No one but the orderly, Harry Kellam (Monte Markham), has heard his confession. When Kellam tells the guard (Al Harrington) and Dr. Sam Berman (Sorrell Booke) what he has just heard, they don't believe him. This so enrages Kellam that he snatches a riot gun from the guard and takes the doctor hostage. He then demands that McGarrett reopen his case and prove him innocent. If McGarrett doesn't, Kellam promises to kill the doctor.
McGarrett begins the search for new answers by reviewing the evidence. Meeting with Kellam's lawyer, Craig Wilkie (William Schallert), he is told that Kellam had a strong motive for killing his partner, Tom Cheney. Cheney had been embezzling money from the firm to pay off huge gambling debts. When McGarrett leaves, Wilkie places a call and announces that there's trouble. Hmmm.
McGarrett talks with Ritchie's fellow torpedo, Banyan (Mills Watson), and gets nowhere. Nor does he get any change from a witness to the slaying, Ted Cowan (Richard Roat), whose story got vaguer and vaguer as the trial approached. Then McGarrett and Chin Ho visit Cheney's old gambling haunt and learn that Cheney didn't have big debts. In fact, he was a very successful gambler. Next, an audit of the company books reveals that there was no embezzlement. The books were cleverly manipulated to hide the profits.
Cowan and his wife Freda (Joan Van Ark) debate whether he should stop being afraid and tell the truth. He calls Wilkie, who tells him to come right over. Wilkie then calls his phone contact who unleashes Banyan. Cowan is shot dead at a traffic light. Mrs. Cowan then shares everything she knows with Five-0.
Back at the prison, Kellam is so tired that he falls asleep. The doctor relieves him of the gun but, because he now believes Kellam, is innocent, stays with him and says nothing to the authorities waiting outside. Concurrently, Danny has learned that Wilkie was the big winner when Kellam-Cheney went out of business. It's time for Five-0 to round him up. Unfortunately, Mrs. Cowan has gotten to Wilkie's office first and Banyan has the drop on her. When the Five-0 team arrives, Banyan uses the woman as a shield. Wilkie shoots him in the back, hoping to cover up his part in the in these criminal doings. Fat chance! After Wilkie's arrest, McGarrett goes to the prison and wakes Kellam up with the good news, "It's all over now."
NOTE: This episode featured an impressively subtle acting job by the late Sorrell Booke in his only appearance on Hawaii Five-0. Booke is best remembered for his over-the-top performance as Jefferson Davis "Boss" Hogg on The Dukes of Hazzard. (P.S. Wasn't it a kick to see Patty Duke's "father" play a villain?)