Jaycee is a woman who appeared in the Pilot (episode) and who was Fred Durran's girlfriend.
Upon arriving at the house, Lieutenant Commander Steve McGarrett and Detective Danny Williams got ready to ambush the house, only for Jaycee to storm out of the house with Durran yelling with her. Danny grabbed Jaycee and silenced her but Durran, upon sensing something was up grabbed a machine gun and began shooting with one of his bullets hitting Danny in the left shoulder and sending him crashing out a window where he landed on a car.
After the gunfight that erupted, Steve and Durran got into a stand-off where Durran sought to kill Steve but Danny emerged at the last second, shooting Durran, killing the gunman and leaving Steve annoyed because Durran was an essential lead in his investigation in finding Victor Hesse, the man who had murdered Steve's father.
Jaycee was later seen being handcuffed and as she was led past by an ambulance where Danny was being treated for the gunshot wound to his shoulder, she told Danny that she hoped the gunshot wound hurt with Danny telling the cops escorting Jaycee to be careful because Jaycee bites.