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
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.
