Catherine Rollins won't return to Hawaii Five-0 for season 5, and Steve McGarrett won't handle the separation particularly well.

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McGarrett's (Alex O'Loughlin) longtime girlfriend decided to stay in Afghanistan following last season's "Makani ʻOlu a Holo Mālie" ("Fair Winds and Following Seas"), and Five-0's leader will have to adjust to a new norm.

"He's taking it hard," said executive producer Peter Lenkov, according to TV Guide. "There's still this mourning period, because even though they didn't break up... she chose to stay behind in Afghanistan, and that actually hurts. So it's definitely on his mind."

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The memory of Rollins (Michelle Borth) won't keep the Navy Seal from moving on, however. A new love interest will soon crop up for McGarrett - one that knew his father.

"After [John] died, this woman, on the anniversary of his death, always shows up at his grave to basically thank him for everything he had done," Lenkov said, according to TV Guide.

Find out more when Hawaii Five-0 returns to CBS on Sept. 26 at 9 p.m. ET.

Tags: Hawaii Five-O television CBS