Coast Guard cutter 'Cape Corwin' sails in Honolulu Harbor to intercept a ship found by a Coast Guard helicopter. The sailing yacht seems to be abandoned as it is floating at sea with no direction but is sailing under a French flag. Upon closer inspection, there is a dead man on deck. McGarrett and a Coast Guard Lieutenant (Norman Dupont) board the yacht discovering the man has been shot. The Lieutenant makes his way forward on the vessel as McGarrett goes below deck. McGarrett finds another dead man at the bottom of the steps. The Lieutenant finds two dead rats in a hatchway as McGarrett find the radio out of commission. He keeps looking around finding yet another dead body! In the dining area, he's joined by the Lieutenant who says someone try to scuttle the boat as multiple rats walk over the food left behind. McGarrett notices women's clothing on a bed with a dead rat falling out. He realizes there is something else going on: bubonic plague! He's seen it before in the Korean War but it didn't register when they first boarded. He and the Lieutenant are lifted into the helicopter taken to the Coast Base, specifically the US Department of Health. When they climb out of the helicopter, the Lieutenant hands off a box with the dead rats inside, which are taken into a laboratory.
The 'Cape Corwin' tows the sailing yacht into port where it is decontaminated. Meanwhile, the doctor (Robert Hopkins) has some bad news for McGarrett: every rat tested positive for plague and they have to assume the entire vessel was contaminated and McGarrett and Lieutenant Talbot could be infected. They must be in isolation for two to six days and McGarrett agrees but he needs a command center set up. When the doctor asks why, McGarrett tells him about the three murders and the table was set for six: someone is ashore carrying the plague!
Five-O arrives at the 'Cape Corwin' and its quarry. Along with them is Che Fong (Harry Endo) waiting to board. Danno double-checks everything is good sending Chin and Ben to check the IDs on the bodies while he and Che climb aboard. They go below deck to search with Che bagging the murder weapon and Danno finding the logbook. He goes up top to find Ben returning with the IDs but everything is in French! Danno tells him to take everything to the French Consulate for a translation because the only thing Danno can figure out is the yacht is out of Papeete.
In the morgue, Doc Bergman (Al Eben) guesses time of death for all three is about 12 to 18 hours ago, more tests need to be run. Doc says he can "narrow it down". Danno is hopeful and tells the photographer to run the photos through as soon as he can.
In Che's laboratory, he briefs Danno on the prints and clothing found on the yacht. Che says there are two sizes of men's suits one with a "Marseilles" label while the other is American and none of the clothes fit any of the dead men found. This confirms three passengers along with the women's clothing found. Che confirms the women's clothing found is all the same size and has a list of labels found. Ben walks in with a translated log: she's supposedly has been in Tahitian waters for the last three weeks! Her last logged position put her 600 miles south of Hawaii.
In the isolation cell, McGarrett declares the log a forgery. If the Marie Celine was sailing from Tahiti, she would be on a northwest heading for Hawaii but when she was seen from Makapuu Point and boarded near Koko Head, she was traveling in the opposite direction. McGarrett tells Danno to see the Weather Bureau and the Geodetic Survey to find out what weather and currents played a part in putting her where she was found and possibly a fix for where she was abandoned.
Danno visits the Weather Bureau to find out about the winds. Chin visits the Geodetic Survey about the currents: there is one going around Oahu at about two knots. They feed everything into the computer to retrace where the ship had been. Chin shows up at the isolation cell to tell McGarrett the news: abandoned between Kahuku Point and Kaneohe three to four miles offshore.
McGarrett's next call is to the governor telling him the bad news: the three passengers are on Oahu. The governor wonders if there's a chance of a mistake with McGarrett saying they could have made Kauai or they could still be on the lifeboat, the key is finding that. The Health Department is willing to give McGarrett until noon tomorrow to find them. The governor isn't willing to gamble telling McGarrett he'll shut off Oahu at noon tomorrow. At 5:55, McGarrett agrees.
The Cape Corwin moves out as HPD Harbor Patrol and HPD helicopters keep up the search for the Marie Celine's lifeboat so they can figure out where the three missing passengers are. The Coast Guard sends up its helicopter too in order to help.
At Five-O, Danno gets off the phone with Papeete then tells Ben and Duke (Herman Wedemeyer) they don't know the passengers because names arenÕt required for local voyages in French waters. Ben and Duke lament they still don't know who was on board or why she was 2800 miles off course. Chin walks in with a photo.
At the isolation cell, McGarrett sees the photo: Leo Paoli (Nehemiah Persoff) underboss of Midwest syndicate and whose prints were found on the yacht. Paoli is Corsica born and operated out of Youngstown, Ohio but deported back to Corsica in 1969 due to tax evasion. The IRS was certain he had $5 million stashed somewhere on the mainland. He has a long list of arrests from assault to suspicion of murder but no convictions at least until Treasury nailed him. Paoli is a widower with his wife dying just before he was deported. His only other family is a daughter Teresa (Jeannine Brown) who is married to Thomas Brown (Bert Convy) and they're still Youngstown. Danno also says Paoli and Teresa are close with Brown being an accountant for the Midwest syndicate. McGarrett tells Danno to check with Youngstown to nail down the daughter's location and he wants everything on Brown.
Paoli and Brown return to a hotel room where Teresa has taken ill. Brown has airplane tickets for 2:30 tomorrow afternoon and it was the best he could do. Paoli and Brown argue from the word go because Paoli wants a doctor for her but Brown refuses because their plan will lay in ruin. Paoli sneers at him, "you tell me you got a connection on this stinking island. Use it". Brown says Tamaki (Nephi Hanneman) can't help with getting a doctor. Brown says it may be the flu from being in the lifeboat but Teresa is very sick, wheezing as she breathes. She wakes enough to recognize Brown but she is nowhere near out of the woods.
Two boys find a boat a little ways offshore and swim out to it. They board rowing it around with a dead rat behind them!
At Five-O, Danno gleans more information as "they" left Paris for Tahiti the same day Brown and Teresa left Youngstown for Papeete. He and Chin figure a meet where Paoli bribed the captain to sail him to Hawaii and drop him on a beach. From Hawaii, he can return to the mainland like any other tourist and no one the wiser. However, three men have been murdered along the way.
The boys keep rowing as an HPD helicopter closes in on them. The boys are brought ashore where they're taken away in an ambulance as Danno and Che arrive. Ben is already on scene, briefing Danno that McGarrett has been told and about the boat: found empty. Danno tells Ben he needs to go door to door and get help to talk to any witnesses. Che goes over to the lifeboat to begin work.
In the isolation cell, McGarrett calls the governor with the bad news: the missing passengers are on Oahu. The governor readies to order a quarantine and asks if it's possible the passengers are already on the mainland. McGarrett doesn't want to think about those consequences.
The governor addresses the State of Hawaii making the citizens aware of the Marie Celine, her dead crew and that it carried bubonic plague. Brown overhears a radio broadcast of the governor's message. The governor goes on talking about three passengers making their way onto the island presenting a threat and the plague is spread through fleas. However, the survivors can spread pneumonic plague as this is contagious and is spread through airborne particles. The governor urges calm and informs the public immunization centers are being set up to help the public battle the disease. Brown enters the hotel room in a panic and as the governor speaks, Paoli realizes the threat. He screams at Brown to get a doctor and sends him out. The governor declares a full quarantine cancelling all air traffic including private charters and all ships are stuck in port: no one is allowed to enter or leave Oahu. Danno and Chin watch at Five-O and McGarrett watches from his isolation cell.
Chin and Ben arrive with two HPD units to begin canvassing the neighborhood where the lifeboat was found. They split the houses with Chin telling them to talk to anybody and everybody. Meanwhile, Brown makes his way to a mobile inoculation center where people are lining up. Inside, he is able to swipe a pair of inoculations and walks away. He calls Tamaki to set up a meet assuring Tamaki he's not sick and he just got a shot. They agree to meet in ten minutes.
While talking to an older Chinese lady, Chin discovers Brown used her phone about 8:30 Tuesday night. Turns out, the lady uses cabs all the time because she doesn't drive. She knew the Moana Cab Company phone number by heart and gave it to Brown who said his wife didn't feel well and his car broke down. She didn't see Paoli or Teresa but it's a lead. Ben leaves to follow up with the cab company.
Brown and Tamaki meet at a temple with Tamaki wondering why he's there because Brown is all over the TV. Brown is desperate needing to get off the island but doesn't have much money, about $8000 total. Brown wonders if he can get to Hilo because the Big Island isn't quarantined. Tamaki says to Hilo is $25,000 in cash but Brown doesn't have that much. However, Brown talks him into it with $7000 to $8000 down and the balance with $10,000 more when Brown returns to Youngstown. He also tells Tamaki that when the Midwest syndicate decides to move in, Tamaki will be their point man. Because of this, Tamaki agrees telling Brown to call him at 10:30 that night.
Ben finds out some information and relays it to Danno: there were ten cabs on the road that night. Ben also says the secretary is tracking down what they need. Danno tells Jenny to keep the line open awaiting details.
Teresa takes a turn for the worse continuing to struggle to breathe. Paoli tries to encourage her but she keeps wheezing until it stops and she dies. Paoli freaks trying to rouse her but she's gone. Meantime, Ben gets the information he needs from Harry Stack who is waiting on them at Pier 7. Danno runs out of Five-O to meet him. Harry recognizes the photos Danno has. He also says there was a lady with them who wasn't feeling well. He dropped them at the Royal Palm. Danno takes off wanting a patch to McGarrett.
At the Royal Palm, Paoli poses Teresa on her deathbed. Brown returns with the inoculations but it's too late. Paoli accuses Brown of planning to take his money then kill Paoli but Paoli plans to turn the tables on him when they get to Ohio. They don't get that far as Brown shoots Paoli twice killing him but not before Paoli spits on Brown giving him the plague! Paoli collapses onto Teresa but Brown figures he's in the clear because he's had a shot. He turns over Paoli ripping the safety deposit box keys off his neck.
At the isolation cell, Danno and Chin brief McGarrett on the latest: "Paoli took two slugs in the chest, Steve. His daughter died of pneumonic". They barely missed Brown and McGarrett wants the APB updated to armed and extremely dangerous. The room is still being decontaminated so Che hasn't had a chance to find anything yet. McGarrett tosses a theory to Danno: Brown is trapped and has to get out but going to the local syndicate is out of the question. However, the locals keep syndicate muscle on the payroll and they know who each other is, even the police know who they are. Is it possible Brown knows too? The main question then becomes who does he know? Danno leaves to check the intelligence files.
Brown shows up at an adult theater while Five-O goes over the possibilities. TheyÕve gone through five with no success but there are still two more. Duke tells the computer operator (Walter Yoshimitsu) to bring up the next guy: Tiro Tamaki. Ben says he knows him and he takes multiple trips to Las Vegas every year. Chin adds he's strictly freelance. The next guy, Eddie Makali, makes a phone call once a month to a New Orleans boss named Moeller and that's the end of the line. There's no Midwest connection with any of them so McGarrett tells them to split up and track them all down and skip the conversation!
At the theater, Brown keeps his head down slipping out to call Tamaki. Brown tells Tamaki he's at The Rose and they'll meet at 6:00 after agreeing to a $7000 ride. Meanwhile, the team slowly whittles the list down with three checked off. Duke crosses another off the list for Danno and yet another is on the mainland so they are down to two. However, Morro had a run in and wound up with two broken arms. They are now down to one: Tamaki who is a problem because he's a social butterfly in the worst way living with four women in the last six months.
Tamaki leaves his current house for The Rose with Ben bringing up the rear. Ben radios Danno what's going on and he lets McGarrett know too. Ben follows him to The Rose and Danno tells him to take him as he leaves Five-O with Chin and Duke. Tamaki takes Brown's money telling him the helicopter will be at Makapuu Point at 7:00, land for 60 seconds and take off. Brown is now stuck trying to figure out how to get to Makapuu Point in an hour as Tamaki walks away. Brown is about to follow Tamaki out until he sees Ben then Brown high-tails out the back. He grabs a cab and takes off. Meantime, Ben frisks Tamaki as Danno, Chin, Duke and two HPD units show up. Danno orders a search of the inside walking to Tamaki asking about Brown. Danno tells Ben to book Tamaki but what's the charge? He's in a No Parking zone! Danno adds that Tamaki needs to be checked out at the hospital, which freaks Tamaki out. Tamaki says Brown told him he had a shot but Danno has bad news for him: "one shot of tetracycline isn't worth a damn to a guy who already has the plague". Tamaki realizes he's been had and tells them Brown is on his way to Makapuu to catch a ride to Hilo. They take off.
Brown walks in the middle of nowhere at Makapuu as the helicopter flies inbound. As the helicopter circles, Five-O and HPD are inbound with sirens wailing. Brown runs to the helicopter stopping long enough to see Danno park behind him. He keeps running when Danno yells at him but he reaches the helicopter and they shoot at each other with Brown being hit and held on by his sleeve dangling from the helicopter. It takes off but the sleeve rips and Brown plunges to his death in the ocean below as Danno, Chin and Ben watch. Danno radios McGarrett the threat is over with McGarrett telling him, "good work". He then phones the governor, "you can open the store".
This plot summary Copyright Bobbi Baker ©2019. No reproduction of any kind without permission.