"There’s a big 'something' that we’ve been talking about for four and a half years that finally gets resolved," revealed series star Alex O’Loughlin.
It’s an emotionally charged episode, and O'Loughlin told ET that his character has to deal with much of the turmoil without the help of his Five-0 teammates.
"I was kind of separate from the rest of the crew for the episode," O’Loughlin dished. "When everybody sees it, you'll see that my character is out doing something else. I’m not around."
Since the show’s premiere in 2010, the cast has also undergone some major real-life changes. O'Loughlin married girlfriend Malia Jones earlier this year, and co-star Scott Caan welcomed his first child, daughter Josie James, in July 2014.
"I try not to give him any unsolicited [parenting] advice," said O’Loughlin, who is a father of three. "Sometimes he comes through with a question or two."