Christine Lahti has joined Hawaii Five-O. The Emmy winner will play Doris McGarrett, the mother of Alex O’Loughlin’s Steve McGarrett, during the next season of the CBS drama. “The mysterious character of Doris McGarrett is a pivotal one to the mythology of our show. We are thrilled to have a seasoned and beloved actress such as Christine to portray her,” Hawaii Five-O executive producer Peter Lenkov said today. CBS renewed Hawaii Five-O for a third season earlier this spring. Lahti is repped by ICM Partners and Management 360.