Alex O'Loughlin missed some filming as he was seeking drug treatment for pain management medication during the production season.

After Steve McGarrett is arrested for Governor Jameson's murder, Danny brings in Joe White to help clear him.

Meanwhile, Chin Ho realizes Kono logged onto HPD's database with his password, which she is using to grant Delano access.

Five-0 investigates the death of a volleyball coach, which leads them to a married couple where he stayed, Carl and Trisha Joyner.

When Five-0 arrests Kono, Captain Fryer of Internal Affairs reveals she is working undercover to stop Delano.

The first crossover event took place in the sixth episode, entitled "Ka Hakaka Maikaʻi" (or "The Good Fight" in English), Daniela Ruah made a guest appearance as her NCIS: LA character Kensi Blye; the episode aired on October 24, 2011.

[29] Chris O’Donnell and LL Cool J appeared as G. Callen and Sam Hanna in the twenty-first episode of the season titled "Pa Make Loa" ("Touch of Death") on April 30, 2012.

[24] In the second part, Scott Caan and Daniel Dae Kim appeared in the NCIS: Los Angeles third season episode "Touch of Death" which aired on May 1, 2012.

[41][42] On July 12, 2011 it was announced that Lauren German had been cast in a recurring role, beginning in the second episode, as Special Agent Lori Weston, a potential love interest for Alex O'Loughlin's character Steve McGarrett.

[7] Larisa Oleynik who also recurred in the first season reprised her role as former CIA operative Jenna Kaye[44][45] William Baldwin also guest starred in a multi-episode story arc.

[46] On August 18, 2011 it was reported that Daniela Ruah would guest star in a crossover episode as her NCIS: Los Angeles character Kensi Blye.

[49] During a second crossover event later in the season LL Cool J and Chris O'Donnell also appeared in an episode as their respective NCIS: Los Angeles characters Sam Hanna and G.

[50] On March 2, 2012, CBS announced that O'Loughlin would miss shooting some episodes of Hawaii Five-0 to seek drug treatment related to pain management medication prescribed after a shoulder injury.

[55] Kevin Yeoman with Screen Rant stated about the series premiere "Hawaii Five-0 managed to do what it does best in the season 2 opener: move at such breakneck speed that the audience hardly has time to recognize the implausibility of it all" and that "The plot of ‘Ha'i'ole’ is paper-thin, as are the majority of the characters and their motivations".

[56] Jim Garner at TV Fanatic says "I have to hand it to Peter Lenkov, he certainly knows how to shake things up and give us a dramatic ending".