CBS has published the press release for the Hawaii Five-0 episode 16 Kekoa that will air on February 11 at 10:00-11:00 PM, ET/PT . The name of Summer’s character is Maggie Hoapili. Here is the short synopsis:

FIVE-0 INVESTIGATES THE MURDER OF A TRADITIONAL HAWAIIAN FIGHTING MASTER AND McGARRETT HIRES A PRIVATE INVESTIGATOR TO FOLLOW HIS MOTHER, ON “HAWAII FIVE-0,” MONDAY, FEB. 11

“Kekoa” – Five-0 investigates the murder of a Lua (ancient Hawaiian hand-to-hand combat) master, and McGarrett hires a private investigator to follow his mother, on HAWAII FIVE-0, Monday, Feb. 11 (10:00-11:00 PM, ET/PT) on the CBS Television Network. Christine Lahti returns as Doris McGarrett. Treat Williams guest stars as a private investigator hired by McGarrett to follow his mother, and Summer Glau guest stars as the daughter of the Lua master who comes to Five-0 for help.
(*Kekoa is Hawaiian for “Warrior”)
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Summer Glau (Maggie Hoapili)
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Source: CBS Press Release