The feud between Gabriel (Christopher Sean) and the Hawaii Five-0crew is about to come to a head - and the villain may pose a greater threat than ever.

After a somewhat lighthearted Valentine's Day-themed episode on Feb. 12, things will take a dark turn on Five-0 when Gabriel returns with a vengeance in an episode airing later in the month.

"He and Chin finally face off in a real significant way," showrunner Peter Lenkov tells TVGuide.com. "He comes back in a way that, it's do or die time for us."

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Another "huge" episode in the Gabriel story line will air as the penultimate installment of the season, Lenkov teases. And, on a perhaps related note, an April episode will have "significant" implications for Adam (Ian Anthony Dale) and Kono's (Grace Park) relationship, Lenkov teases.

Will the team be able to get rid of Gabriel once and for all - and if so, at what cost? Fans should brace themselves for "a lot of action and some big surprises," according to Lenkov. Sounds ominous!

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