A powerful run is up ahead for "Hawaii Five-O" season, and CBS has been generous enough to share the storyline of the season's first episode.

Steve McGarrett's (Alex O'Loughlin) life was in grave danger during the previous season's finale and it required Danny Williams (Scott Caan) to donate half of his liver to keep him alive. In the upcoming season's premiere, Steve refuses to slow down despite the surgery and it looks like he and Danny will continue with the love-and-hate-brotherly relationship banter they are known for.

Fear looms over Hawaii when a serial killer's body is found with an ivory chess piece in his mouth. When a second serial killer is found dead with another chess piece, the team works on the case to hunt for the perpetrator. Alex refuses to slow down, but he finds comfort when someone with a special connection to the team engages him in a conversation.

The premiere will feature two recurring characters, Governor Keiko Mahoe and Alicia Brown. Actress Rosalind Chao plays Governor Mahoe, while actress Claire Forlani plays retired criminal profiler Alicia.

Viewers are also looking forward to the re-appearance of actress Christine Lahti who plays Steve's mother, Doris McGarrett, on the show. She will appear during the 150th episode special to take care of her son.

Another story fans of the show look forward to in the season is the reconciliation of the seemingly star-crossed lover Kono Kalakaua (Grace Park) and Adam Noshimuri (Ian Anthony Dale). The two's love for each other has been proven many times on the series, but Kono's dedication to her career and Adam's past always come between them. A healing is said to happen, but the road to recovery will not be easy.

"Hawaii Five-O" season 7 premieres on Sept. 23 at 9 p.m. on CBS.