Magnum is training for an Iron Man. Higgins and the pups join him on the beach. She's training for the Iron Man too.
He gets a phone call from a client and leaves. Higgins knocks on his door to tell him that his client is at the gate.
A woman wants Magnum to find her cousin, Sergei. She doesn't want to file a missing person's report and she wants to hide the fact she's in the U.S. which is why she went to him.
Sergei is a missing journalist.
He's being followed when he leaves to investigate. Rick shows up. They go to a Russian restaurant to ask about Sergei.
The chef has seen him as he comes in a few times a week. Rick stays behind to eat, but Magnum leaves and the guys are still there who followed him so he goes up to their car. They hit him and speed off.
Rick comes out and the two of them take chase. The cops show up and the other guys start shooting but then get away. Magnum and Rick get pulled in.
Katsumoto questions Magnum and he tells Katsumoto about his case briefly. Katsumoto is going to let him go but this is his last chance. He's not bailing him out again.
T.C. is there to pick them up and warns them that they're going to go to jail one day and he and Rick go down the list of all the illegal stuff Magnum has done.
Magnum shows up back at the house and the Ferrari is filthy. Higgins wants to know why. She's there with the dogs and Kumu.
Higgins is complaining about how Magnum is cleaning the car and he takes off his shirt to dry the car. Kumu says she's happy for that. Higgins says nothing.
The restaurant guy calls Magnum to tell him that Sergei is at the restaurant. Magnum tells him to stall Sergei as he heads to the restaurant. On the way, he calls Katia. The restaurant guy is stalling Sergei but Sergei takes off just as Magnum arrives. Magnum takes chase but can't find him. He calls TC to see if he can help and he obliges.
Now Magnum is being chased by the two guys who have guns. Magnum finally catches up with Sergei but Sergei wants to get something even though there's no time. It's a suitcase. The bad guys are coming up the stairs but Magnum and Sergei go the other way. TC has to go because his fuel is low so Magnum is on his own. Katia shows up at the estate and Higgins answers the door and sees two bad guys there so she runs a scan on Katia.
Magnum calls Higgins and learns that Katia is really an ex KGB officer. The real Katia is dead. Magnum heads to HPD. Higgins will deal with the situation on her own. Katia somehow got into the house under Higgins' nose.
And there's a fight between them. A KGB agent versus a former MI6 agent.
Kumu comes to save Higgins but he two bad guys show up and Kumu's gun is taken from her.
Sergei tells Magnum about his cousin. Magnum gets a phone call from the bad guy. They want Sergei in exchange for Higgins and Kumu. Sergei pulls a gun on Magnum and kicks him out of the car and takes off.
Rick picks up Magnum and TC is looking for Sergei. Meanwhile, Higgins and Kumu are being held prisoner.
TC finds Sergei. Rick and magnum take chase. The cops chase after Rick and Magnum for speeding. Magnum calls Katsumoto for help.
Katsumoto calls off the cops. They catch up to Sergei.
Sergei has a nuclear bomb in the suitcase and that's what the bad guys want. Sergei explains why he has the bomb. He was going to destroy it.
Magnum and Rick show up at the estate. Sergei isn't with them. Magnum shows them the suitcase.
The dogs are in Kumu's van and attack the bad guys, saving Magnum. Meanwhile Higgins kicks KGB girl's ass. Magnum releases Kumu and tells Higgins about the device.
Katsumoto arrives at the estate and Magnum thanks him for helping out. Katsumoto's team is going to get rid of the nuke.
Sergei arrives at the estate and reminicses about Russia and how he is going to make Hawaii his new home. And he's made a friend in Magnum.
Higgins shares a story with Kumu.
Higgins and Magnum run on the beach and engage in a race.