'Hawaii Five-0' season 7 spoilers, plot news: Catherine returns; 'more complex' villain emerges

There's a chance that Catherine (Michelle Borth) and her ex, Steve McGarrett (Alex O'Loughlin), will be rekindling their romance in "Hawaii Five-0" season 7.

Catherine is said to be returning in an upcoming episode of the current season. "Hawaii Five-0" executive producer Peter Lenkov recently told TV Guide that Borth will be back for the show's landmark 150th episode. Whether or not she will stick around after that is unclear, but Lenkov teased that Steve's "attitude toward the relationship is definitely reflective of what he's been thinking the [previous] few episodes."

As fans recall, Catherine, a former Navy Intelligence officer, had bid Steve goodbye in season 4, when she decided to stay in Afghanistan and continue her search for the son of the man who saved her life in Kabul. She reappeared in the season 5 finale, in which she once again left a heartbroken Steve. But strangely, she was later shown talking to an unidentified person and informing the character that Steve bought her story.

Catherine will play a pivotal role in the CBS police procedural's 150th episode, which is said to tell the story of Steve's mother Doris (Christine Lahti), her relationship with her son, and her connection to the late Wo Fat (Mark Dacascos).

Speaking with Entertainment Weekly, Lenkov recently said that episode 150 will dig deep into these characters and show Steve's relationship with his mother when he was a little boy. The episode will shed light on Doris' character and will have Steve thinking back to the time before she abandoned him.

"That's going to make him think back and we're going to see moments of McGarrett and his mother when he was little, and the fact that she was this caring, mother next door, she was somebody who adored her son, would never give up her family," he said.

Meanwhile, the Five-0 team will soon be dealing with a new villain with ties to the serial killer they are currently tracking down.

"It's a very different big bad," Lenkov told TV Guide. "Somebody a little bit more cerebral, a little bit more complex than anybody that we've dealt with before."

"Hawaii Five-0" airs Fridays at 9 p.m. EDT on CBS.