When Hong, a man that Magnum and Higgins are monitoring for a client, gets shot and killed and his killer escapes, the team from Hawaii Five-0 gets involved.

Magnum, Higgins, TC and Rick assist as the group recovers a secret list of CIA double-agents.

Soon after, Junior Reigns is kidnapped as leverage for the criminals to get the list back, leading to Magnum's team helping Tani Rey and Quinn Liu in a search-and-rescue mission.

[22] On September 9, 2019, TVLine reported via an interview with Lenkov that a story for the crossover had been developed and that he intended on making it happen sooner than later.

[27] Peter M. Lenkov returned to the series as executive producer and co-showrunner after signing a three-year deal with CBS Television Studios in 2018.

[30] On the November 15, 2019, episode, "He Came by Night," the band Train with artist Skyler Grey made the first public performance of their new song "Mai Tais" on the series.

[37] A new filming location in the season is the La Mariana Restaurant, an operating Tiki Bar in Hawaii.

[39] Numerous professional athletes appeared in guest roles throughout the season including Deontay Wilder, a World Boxing Council heavyweight champion, Aaron Donald and Andre Reed, National Football League players, Hans Hedemann, a competitive surfer, and Cowboy Cerrone, an Ultimate Fighting Championship mixed martial artist.

[43][44][45][46][47] Patrick Monahan, Skyler Grey, Jerry Becker, and Luis Carlos Maldonado appeared as themselves and performed as their real world band Train.

[40] Betsy Phillips, series star Zachary Knighton's wife, appeared in the seasons final episode.

[24][52][53] In addition, other Hawaii Five-0 guest stars including Larry Manetti, William Forsythe, Shawn Mokuahi Garnett, Willie Garson all appeared as their characters as well.

[57] The annual event known as "Sunset on the Beach" took place on September 18, 2019, and featured a performance form the band Train.

[61] Following the timeslot being freed up by the Hawaii Five-0 series finale, the season continued airing its remaining six episodes on April 10, 2020.