Willy Stone (Moses Gunn) is a washed-up ex-boxer reduced to selling newspapers in front of the Honolulu sports arena. As two fighters prepare for the weigh-in before their match, Stone tries to speak to one of them, Robby Davis (Henry Porter). He is brushed off by Davis’s manager Cal Phelps (Robert Costa) and others. Stone later enters Davis’s dressing room and smashes the sleeping fighter’s hand with a wrench.
Mobster Matty Edmonds (Albert Paulsen), a man with an "interest" in the injured fighter, arrives from Detroit and is met at the airport by McGarrett. McGarrett asks why Edmonds has come – since he has a record, he can’t manage Davis. Edmonds tells McGarrett that he has some to Hawaii for "some sun and some broads." McGarrett gives Edmonds a stern warning, telling him "don’t even spit on the sidewalk."
Edmonds meets with Dr. Fukata (Seth Sakai) who says that Davis’s hand is destroyed and will take a lot of time to rebuild … and then it will still not be functional for boxing. When Edmonds tells him to spare no expense in fixing the fighter’s hand, Fukata says that Davis won’t fight again. Edmonds calls him a quack, and demands to speak to another doctor from the university who is a recognized authority on such injuries. After Fukata leaves, Edmonds abuses Phelps for not watching Davis more carefully.
Edmonds visits a local thug and offers him money to find Stone.
At the Five-O office, Kono tells McGarrett that Stone has disappeared. McGarrett wants "the book on him," and tells Kono to tail Edmonds.
In his hotel room, Edmonds talks to Phelps about Davis, saying the fighter was their "greatest prospect." Edmonds is obsessed with finding Stone, and Phelps says "you’re going crazy." Despite Phelps’ pleading not to involve the syndicate, Edmonds phones Detroit and asks for them to send a hit man.
At the Five-O office, Chin Ho reports that Willy Stone had 20 fights on the island. Chin is called away to the Kahala Hilton, where a telephone operator briefs him on the conversation she overheard between Edmonds and the Detroit mob regarding the hit man.
McGarrett visits Edmonds who is getting a massage at his hotel pool. McGarrett gives Edmonds a warning not to try and go after Stone.
Stone comes to the restaurant run by "Mama" (Mama Luna) and begs her for some food.
Back at the Five-O office, the men look over some mug shots which Detroit police have sent them. At the airport, Kono, Danno and Chin watch for the hit man, but he is a young blonde man, Duke (Frank Webb), who doesn’t match any of the photos. Kono reports to McGarrett that they have missed him; McGarrett says "there’s a soldier on the rock."
Danno goes to Willy’s place and looks through his memorabilia. Among the items he finds are a couple of cans of film of Stone’s fights.
Back at the office, Chin Ho gets a tip to check on "Mama." He goes to her place with Danno, and she asks them "What’s the rap, selling sausage without a license?" Chin and Danno persuade her to tell them where Stone is hiding out – at a bar called Mae’s Place.
McGarrett, accompanied by the other members of the Five-O team, drops in to the bar and tells the owner Mae (Lynn Hamilton) that "if I don’t get to Willy first, he’s pau"; She says Willy knows someone wants to kill him and he’s scared. Willy is hiding in the basement of the bar, and McGarrett goes downstairs and talks to him, asking "Why did you do it?" Willy replies only, "I knew I had to… I did it for that kid." McGarrett convinces Willy to surrender, but on their way out Willy punches McGarrett and escapes.
Willy runs out of the bar and is pursued by Danno. Stone jumps over a fence, leaving Danno in the dust. On the street shortly after, Stone is recognized by a punk, Fred (Ah Vah), who confirms his identity with the help of his girl friend Luella (Josie Over). When he sees Stone going in the direction of the Civic Auditorium, the punk calls Edmonds, who is overjoyed, saying "you just made yourself a thousand."
At the hotel pool, Edmonds is anxious to get Stone, but Duke is in no hurry, saying they should let Willy "sit and sweat."
At the auditorium, the janitor (Lippy Espinda) says that Stone can sleep in the office over the weekend. The janitor says that Stone should give himself up.
Back at the Five-O office, McGarrett and Danno watch the films of Stone’s fights. Kono is pursuing Edmonds, who leaves his hotel and who picks up Duke on the street. Kono tails the two of them, but loses them at a red light when Edmonds and Duke abandon their car, causing traffic chaos.
At the auditorium, Duke picks a lock to get himself and Edmonds inside (a woman oversees this and calls the cops). They find Stone in the boxing ring, where Edmonds wants to know why he smashed Davis’s hand before Duke knocks him off. Stone says "I just had to … I never meant to harm that boy … I loved Robbie Davis … he couldn’t have made it ."
Edmonds orders Duke to shoot Davis, but as Edmonds is on his way out of the auditorium, Duke shoots him fatally, saying "the contract was always on you … you should have known your operation," telling Edmonds he was "unreliable" and "flipping out" for wasting the syndicate’s time with such a trivial matter.
Duke exits, but there are shots heard outside the auditorium and Five-O rushes inside where McGarrett again asks Stone again for an explanation. Willy says that Davis "would have ended up just like me." When he asks McGarrett what kind of treatment he can expect from the courts, McGarrett says, "I’ll do the best I can."