After a brief hiatus last week, Hawaii Five-0 season 9 returns with a fresh episode on CBS. Viewers, however, need to brace themselves as the upcoming installment will be a stormy ride.

There's a hurricane that's about to strike Oahu in Hawaii Five-0 season 9 episode 15. The locals are forced to evacuate and to find a safe place, including Charlie (played by Brian Yang) and Rachel (played by Claire van der Boom), who head to the house of Danny (played Scott Caan). 

Forced to stay with each other until the hurricane passes, Danny and Rachel reminisce about their past relationship, as per The Futon Critic. It's a sensitive time for the ex-couple on Hawaii Five-0 as they have just undergone a heart-breaking and stress-inducing custody battle for their daughter Grace (played Teilor Grubbs).

It's no secret that there's been a lot of tension between Danny and Rachel. Though they have not been together for years, the conflict between them continues to pile up on Hawaii Five-0. Among the biggest problem that the ex-couple can't seem to agree with is Rachel's desire to move to Nevada to be with her new love Stan (played by Mark Deklin). Danny fought her in custody because he didn't want his ex-wife to take Grace away from him.

Fortunately, Danny won his case in court but Rachel continues to resent her ex-husband for it. As the weather outside increasingly becomes dangerous, the tension between the ex-couple gets heated at Danny's house. But will Hawaii Five-0 season 9 episode 15 finally give the couple some peace and closure or will there be more tension after the hurricane is gone?

It looks like Danny and Rachel's problem won't be completely over as Rachel's mother is still expected to pop up in an upcoming episode. As reported by TV Line, legendary TV star Joan Collins is set to appear on Hawaii Five-0 season 9 episode 18 as Rachel's mom, Amanda Savage. Now, Amanda isn't particularly fond of Danny but she will apparently love her ex-son-in-law's partner, Steve McGarrett (played by Alex O'Loughlin). 

Meanwhile, Hawaii Five-0 season 9 episode 15 will also delve with a captured serial killer whose life is threatened by an assassin. McGarrett and his team have to protect El Diablo (played Raoul Trujillo) in the middle of this dangerous hurricane, while Tani (played by Meaghan Rath) is tasked to do safety checks among the civilians. 

Hawaii Five-0 season 9 airs Friday nights at 9:00 p.m. on CBS.