When the CEO of a surf company is found murdered, Kono revisits her past and Five-0 is thrown headlong into the interconnected worlds of North Shore surfing.
Charlie is now dating Kandi's (recurring guest star April Bowlby) mother, Mandi (recurring guest star Gail O'Grady). Meanwhile, Alan is depressed because Kandi has left him and is staying with bitter Judith, who brainwashed her against him. At Mandi's urging, Alan goes to Judith's place to try to win Kandi back. Also, Kandi introduces Judith to Kandi's father, Andy (Kevin Sorbo - "Hercules: The Legendary Journeys," "Andromeda").
As the new year approaches, Ryan plans a special surprise road trip for Taylor and himself, but when Summer confronts Seth about not making any plans, Ryan's romantic getaway for two is spoiled. Later, Summer's future rests in the hands of a shady character that the gang meets on the way to Las Vegas. Meanwhile, Julie's accounting practices come under some unwanted scrutiny.
Newly engaged Seth and Summer both panic about the prospect of being married, but neither will break it off, despite the advice of their friends. Instead, they begin a complicated game of one-upmanship that almost leads them to Las Vegas for a wedding. Meanwhile, when Ryan's estranged biological father, Frank who has been in prison for years, tries to reconcile with Ryan, Sandy remains dubious.
Ryan, the Cohens, the Coopers and their friends build new lives, resolve lingering issues, face major decisions and undergo shocking personal transformations. No matter what happens or where they go, the members of this unique extended family all know that they will always have one another to turn to.
