A decorated former Navy SEAL who, upon returning home from Afghanistan, repurposes his military skills to become a private investigator in Hawaii.

Magnum helps Dan, a struggling fisherman and fellow veteran, when his 300-pound tuna worth $350,000 is stolen, and he discovers that the thief needs Magnum's help as well.

Magnum takes a case from fellow private investigator Luther Gillis to find the true identity of a man’s comatose fiancée when he learns that she’s had extensive facial surgery.

A close friend of Higgins, an art connoisseur who recently hired Magnum to test his security, is murdered, and Thomas is arrested as the main suspect.

TC asks Magnum to take on a case to help acquit the father of one of his young football players, who is accused of murder.

An aging tycoon asks Magnum to find his lost love who he says just recently contacted him; the only problem is she died 30 years ago. Also, Rick and TC meet a fellow vet who is having a hard time adjusting to civilian life.

Magnum takes the case of a little girl’s missing cat and, in the process, stumbles upon another cat’s murdered owner who happens to be an FBI agent.

A man dying of lymphoma hires Magnum to find his estranged, bone-marrow-compatible brother who turns out to need Magnum’s help as well. Also, Magnum’s case brings back haunted memories for the guys of a past SEAL team mission that went sideways.

After a 16-year-old kidnap victim, Amanda, escapes her captors, her parents hire Magnum, who experienced similar trauma as a POW, to find who took her.

Magnum must help Rick’s crush, Toni, after her illegal poker game, organized to pay back a mob debt, is robbed by masked gunmen.

As Magnum helps a woman find her missing cousin, Sergei, a Russian fugitive, Higgins' and Kumu's lives are put in danger when they get too close to the case.

Magnum has an emotional connection to a case when he and every other private investigator and bounty hunter on Oahu are tasked to track down a man accused of murder.

Magnum and Higgins are shocked when one of her former MI6 teammates shows up with a fresh gunshot wound and news that "the Viper," the assassin who killed Higgins' true love, has surfaced on Oahu. Also, while Magnum's busy helping Higgins track down the Viper, he asks Rick to take over a case, a task that Rick relishes until it goes sideways.

A man hires Magnum to investigate his own murder before he is killed. Kumu reconnects with an old friend.

Magnum discovers that his ex, who landed him and his friends in a POW camp, is on the island and planing to steal a fortune in gold.

Magnum is hired by a woman to prove that her son didn't kill his girlfriend and has only 24 hours to do so before the accused accepts a plea deal. Also, Rick and TC try to recover stolen appliances that were donated to a wounded veteran.

After a man is murdered, Magnum poses as a doctor on the same dating app the victim was using in order to find the killer who may be praying on wealthy men.

When the Dobermans dig up what appears to be a human bone, Magnum and Higgins help Katsumoto investigate the murder of his former mentor.

When Magnum and Higgins get “yacht-jacked,” Higgins is shot and she and Magnum are stranded at sea, struggling to reach land before she bleeds out and the culprits return to finish them off.

Hannah, Magnum's ex and the fugitive responsible for him and his SEAL team brothers being POWs for years, shows up at his home with a gunshot wound, and wanting his help to find her missing CIA father whose life is in danger. Also, Magnum makes an earnest proposition to Higgins for her to become his private investigations partner.

While Magnum waits for Higgins to decide if she’ll officially become his partner, he takes the case of a missing wife who witnessed her boss’ murder during a bank robbery. Also, Rick makes a big decision about his career.

An incorrigible pickpocket, Jin, asks Magnum for help when a cell phone he recently lifted receives a very suspicious text message. Also, Magnum is frustrated when Higgins still won’t give him an answer to whether or not she will become his partner, and when Rick decides to make a bold career move, T.C. comes to the rescue.

Kumu and Higgins are in danger when Robin's Nest is under siege by mercenaries storming the estate in order to find out the true identity of the White Knight, Robin's muse and literary hero. Also, Rick and T.C. helps one of Rick's employees when his car is stolen, and Higgins finally gives Magnum an answer about if she'll become his partner.

When Katsumoto suspects that one of his fellow cops is dirty and has stolen evidence, he begrudgingly asks Magnum and Higgins for help. Also, Rick and TC help Los Angeles Rams defensive tackle Aaron Donald when his tablet, that contains the Rams’ playbook is stolen.

On Halloween, Magnum and Jin search for a skip-tracer at a Halloween bash, just as Katsumoto tracks an escaped killer who is headed to that same party. Also, Higgins and Rick must spend the night at an allegedly haunted house in order to debunk the notion, and TC and Kumu protect a sacred Hawaiian burial ground.

Magnum must help his defense attorney girlfriend, Abby Miller, when she realizes that the client she successfully defended in a murder trial is actually guilty. Also, TC confronts Kamekona about stealing his helicopter business.

While Magnum helps out his friend Russell Harlan and temporarily works as the head of a hotel’s security, he investigates the death of a guest who was thrown from her room’s balcony while working on a secret investigation of her own. Also, Icepick is released from jail and is trying to keep a secret from Rick.

Magnum and Higgins' new partnership is tested when they disagree about being hired by a woman who wants them to recover her $3 million in stolen drug money in order to save her husband's life.

A guilt-ridden Magnum follows the clues his private investigator friend, Harry Brown, left behind when he was shot while working a case Thomas passed onto him. Also, TC helps Kumu lead a protest against construction on a Hawaiian sacred site.

Magnum, flooded with memories of his tour in Afghanistan, helps his fallen friend’s brother search for a now-grown Afghan boy who may have been a victim of trafficking.

Magnum is called up from the reserves for a top secret mission, but his friends are stunned when they learn that the mission is a lie and Magnum has been set up.

When Junior is kidnapped as leverage to retrieve the stolen list of undercover CIA agents, and most of Five-0 is rounded up by the CIA to prevent them from interfering, Tani and Quinn ask Magnum and Higgins for their help.

The crossover starts on Hawaii Five-0 S10E12 Ihea ‘oe i ka wa a ka ua e loku ana? (Where were you when the rain was pouring?) (I).

Magnum and TC go undercover as efficiency experts when a corporate manager is murdered and everyone in the office is a suspect. Also, Rick is curious why Higgins faked an injury to prevent her from investigating the case with Thomas

When Jin learns that an innocent woman is the target of a deadly hit, he asks Magnum and Higgins to help save her.

Magnum and Higgins must find Kumu when she's kidnapped by an injured man accused of killing his wife.

While Magnum and Higgins are undercover as a couple on a romantic bus tour working a case, they must switch gears when one of the love birds on the trip is murdered and evidence is quickly deteriorating in the Hawaiian heat.

Magnum and Higgins take the case of recovering the stolen urn of a woman's deceased husband, but they soon find that others believe the urn is worth killing for. Also, Rick and TC confront a man who's been impersonating football legend Andre Reed.

As their wedding day approaches, Magnum and Higgins help a modern-day Robin Hood who, thinking she was helping a school obtain needed supplies, unknowingly stole illicit drugs. Also, Rick helps a retired soldier with the difficult task of re-entering the work force as a civilian.

Magnum and Higgins are each hired by a different spouse who are in the middle of a contentious divorce to dig up dirt on the other, and Thomas and Higgins soon find themselves competing over resources. Also, Rick and TC look into the death of an unidentified man and must share the news with his estranged daughter.

Magnum and Higgins help Rick when his father figure, Icepick , just out of prison and battling terminal cancer, gets double crossed on one last score. Also, Magnum makes one last bold move to help Higgins stay in the country.

Magnum and Higgins’ new clients hire them to find their missing brother last seen on the island, leading to Higgins being shot and TC abducted when a secret case of revenge is revealed during the investigation. Also, Higgins (and Magnum!) are surprised when her surgeon asks her out.

Higgins job to repo a plane goes south when she and Magnum discover that it was being used by a drug cartel who opens fire at the plane, forcing them to crash land in the jungle, where they find a stowaway on board with a target on his back. Also, Higgins has her first date with Dr. Ethan Shah.

As Magnum, Higgins and TC try to pull one over on a customs agent to get Higgins a green card, armed gunmen suddenly storm the federal building and start taking hostages.

Magnum and Higgins help an up-and-coming mixed martial arts fighter who is being pressured by a gang to throw an illegal fight. Also, Kumu is arrested for stealing an artifact from a collector that should be returned to its original resting place.

As a major hurricane hits the Island, Magnum and his friends find shelter inside La Mariana, along with two armed killers also escaping the dangerous storm. Also, Rick must confess to TC that he let the insurance lapse on the bar.

When a wealthy man hires Magnum and Higgins to find his missing wife, they are stunned when a tragedy occurs as a result of their investigation. Also, Kumu's suspicion of her step-daughter's boyfriend creates a divide with her and Kumu's new relationship.

When an overenthusiastic neighborhood watch group asks Magnum and Higgins to investigate a shady character living on their block, they are shocked to find that they may have inadvertently stumbled upon a serial killer on the loose. Also, Jin’s new money laundering business leads him to want to help a new friend.

When a young man in need of immediate emergency surgery goes missing with a bullet lodged in his chest, Ethan asks Magnum and Higgins to find him before it’s too late. Also, TC talks to a military recruit who may be enlisting for the wrong reasons.

When Higgins is abducted, Magnum discovers its retaliation related to one of his first cases on the Island, and he, Rick and TC must break out an ex-client from prison in order to save her.

When an Army ranger goes missing after returning from deployment, Magnum learns of the traumatic news he received upon arriving home and must find him before survivor’s guilt consumes him. Also, Higgins and Ethan solve the case of a missing engagement ring while on a mini-break, and Katsumoto tries spending quality time with his teenage son.

When a married woman asks Magnum and Higgins to find her lover’s killer because she doesn’t want to expose the affair to the police, they find that the victim wasn’t who he claimed to be. Also, Rick visits Icepick, whose health has taken a turn for the worse.

When a Marine Corps vet’s SUV is stolen with her service dog inside, Magnum and Higgins must find the car, the dog and the car thief who they believe may be an escaped kidnapping victim. Also, when TC is sued by a disgruntled customer, he asks Rick and Jin to help prove that he’s being scammed.

As Magnum and Higgins work a case to recover valuable stolen truffles, they also must care for a baby left abandoned at the gates of their estate, while Kumu tries to locate the infant’s mother.

A psychic hires Magnum and Higgins to prevent a murder she claims to have foreseen. Also, Katsumoto questions Kumu when her information is found on recovered stolen jewels that once belonged to the infamous Imelda Marcos, and Higgins struggles with whether or not to tell Ethan the truth about her past.

Magnum’s Uncle Bernardo visits and reveals a shocking secret about Thomas’ mother. Also, TC asks Higgins for help when he realizes he may have witnessed a potential murder from his helicopter, Higgins decides it’s time to tell Ethan the truth about her past and TC offers Shammy the opportunity to become a pilot.

Magnum and Higgins work a stalking case involving a man with a past in espionage. Also, Ethan asks Higgins to join him on an extended trip for Doctors Without Borders just as Magnum starts to open up to other possibilities.