'Hawaii Five-0' season 7 air date, spoilers news: Sarah Carter returns; Five-0 team goes after vigilante in season premiere

"Falling Skies" grad Sarah Carter, who played the role of Lynn Downey, Steve McGarrett's (Alex O'Loughlin) new girlfriend in the previous season, will be reprising her role in the seventh season of "Hawaii Five-0."

The actress will appear in the action/police procedural series' milestone, the 150th episode, as will two other returning cast members playing two other special women in Steve's life, TV Line has learned. Christine Lahti, who plays Doris McGarrett, Steve's mom, and Michelle Borth, who plays Catherine Rollins, Steve's ex-girlfriend, will also be in the episode.

Carter appeared in two episodes in season 6. Her "Hawaii Five-0" debut was in episode 7 when Steve and Lynn went on a first date that went awry. She later appeared in the show's Valentine Day-themed episode, in which Lynn found the ring that Steve had planned on proposing to Catherine with.

Additionally, CBS has reported that Claire Forlani will reprise her role as Alicia Brown, and Rosalind Chao will return as Governor Keiko Mahoe in the "Hawaii Five-0" season 7 opener.

Meanwhile, the "Hawaii Five-0" season 7 opener will be a whirlwind of action, mystery, and danger. The Five-0 Task Force is reportedly going after a murderous vigilante whose actions threaten the safety of everyone in the Aloha State.

In the previous season, Steve and his partner, Danno Williams (Scott Caan), went undercover to put a stop to the meth epidemic. In the process, Steve was seriously injured, and Danno had to break their cover to save Steve's life. Later on, Danno also offered to donate half of his liver to Steve.

In the season 7 premiere, Steve, who is recovering from surgery, will be ignoring his partner and best friend's pleas to take it easy when the body of a serial killer ends up in the Honolulu Police Department with an ivory chess piece lodged in his mouth.

The first body is followed by another dead serial killer, who is also found with a chess piece. The Task Force will go after the unknown perpetrator as word spreads that Hawaii has become unsafe for tourists and residents alike.

"Hawaii Five-0" season 7 premieres on Friday, Sept. 23, at 9 p.m. ET on CBS.