A woman dressed like a widow (Loretta Swit) gets out of a cab and enters a bar where she tells the other women -- Betsy the bartender (Barbara Nichols) and her roommate Yoko Collins (Barbara Luna) -- that she just got $10,000 and she is now "free". They drink champagne. The scene cuts to later, when the woman arrives at her home by cab. She is drunk and drops her purse on the ground. When she stoops down to pick it up, in the foreground we see a man's legs. He slaps her, knocking her out, then drives over her with his car.
McGarrett is at the scene of the accident. The woman had a receipt for $10,000 of GI insurance. She was found face down in the middle of the road, which suggests it was not a hit and run. McGarrett visits the bar where he talks to Betsy about the woman, Anna Stockton Shroeder. Betsy says that Anna -- who was a hostess at the bar -- left alone at 3 a.m. carrying "a lot of bread."
McGarrett orders Kono to check the cab company that brought Anna home. He goes to Yoko's apartment (Yoko was Anna's roomate) and grills her about the suspicious circumstances surrounding Anna's death. Yoko says Anna had a soldier husband whom she married on the Big Island, after which he went back to Vietnam.
McGarrett arranges for Danno to go undercover. Pretending to be "Danny Carson," a pal of Anna's late husband, Danno arrives at the bar, where he asks Yoko about Anna's death. She doesn't want to talk about it. After several drinks, he takes her home. She tells him there were other hostesses who married soldiers -- Sheila and Maria -- both of whom had "accidents" after their husbands were killed in action.
At the Five-O office, McGarrett sends Kono to the City Hall Bureau of Records to check marriage licenses and Chin Ho to the army base at Scofield to check the beneficiaries of the insurance. Danno has a major hangover, and takes what looks like an Alka-Seltzer. McGarrett recommends that he should pour the booze into a plant next time.
At City Hall, Kono finds the information he needs, but only after questions by the suspicious clerk James Watanu (James Hong). While Kono is looking in the file folders, Watanu, who seems very nervous, makes a phone call. At the army barracks, Chin Ho gets a lot of mouth from Sergeant Simms (Harry Guardino), but Chin finally gets what he wants after he threatens to pull rank.
Danno and Yoko frolic at the beach, kissing. She is suspicious when he wonders if the other hostesses were killed for the insurance money.
Watanu visits Betsy at the bar, saying he only predated the marriage licenses and didn't realize what he was getting into. She makes a phone call to Simms, then returns to tell Watanu there will be "no more marriage licenses, no more girls." Watanu takes some medicine.
Later, Watanu goes outside where he encounters Simms who takes him for a ride in a jeep. They stop far away from the city, where Watanu says that Simms has "nothing to fear" since if Watanu told the police, he would be implicated himself. He wants to take a pill for his heart condition, but Simms takes the pill container and throws it away, saying "a thousand pardons..." Watanu tries to find the pill bottle, but collapses and dies as Simms drives away in the jeep.
McGarrett confronts Simms with a piece of tire tread found beside Watanu's body which matches that on a jeep that Simms signed out of the motor pool. McGarrett questions Simms, saying that the predated marriage certificates came through Simms' office. Simms denies knowing Watanu, saying "I don't have any Jap friends."
At the beach, Yoko leaves Danno, having realized that he is not a GI. She tells him, "Every second you spent with me was a lie." Back at the Five-O office, Danno says, "I blew it!" Chin Ho and Kono have found out that Simms is 43, a bachelor and a "loner," and has a perfect service record. Simms was close to his brother Andrew, who was killed in Vietnam, and whose widow also met with an "accident."
At the Army base, McGarrett engages Simms in some verbal sparring over a game of pool. They discuss the fact that Watanu had a heart condition, that Simms' brother's wife died of an overdose of sleeping pills, and that the brother changed his will to make his wife, rather than Simms, his beneficiary. Simms says "he could have killed" his brother's wife, that she "murdered" his brother because he was thinking of her in Vietnam rather than of the enemy when he was shot.
McGarrett convinces Yoko to help him lay a trap for Simms. She calls Simms and arranges a meeting at the bar to concoct another insurance scam. When they get together, Yoko says that Anna told her everything. She withdraws money from a bank and meets Simms at her apartment. Chin Ho is in the next room listening with a microphone. Yoko gives Simms the money. He says that his brother gave up his life for his country, and that he died for "trash" like her. When they exit, the police are waiting. McGarrett orders Simms to give up, but Simms draws his gun and is killed in a shower of gunfire.