EXCLUSIVE: Steve McGarrett’s love life is looking up. Michelle Borth, who appeared in five episodes of Hawaii Five-0‘s first two seasons as McGarrett’s squeeze, will join the CBS procedural as a regular when it returns for a third season in the fall. She will reprise her role as McGarrett’s girlfriend, Lt. Catherine Rollins. Borth, repped by CAA, New Wave Entertainment and Marcy Morris, first guest starred in the fourth episode of Hawaii Five-0‘s first season and was most recently seen in an episode last month. She previously starred on ABC’s The Forgotten and Canadian-produced Combat Hospital. Borth is the second recurring guest star to be upped to regular on Hawaii Five-0 following last year’s promotion of Masi Oka. She joins Grace Park as the second female regular cast member on the show.