Sun Yee was Director of Security at Cleopatra Casino in Hong Kong. He is somewhat short in stature but powerfully built. He was a former member of the Golden Triangle Triad, but he managed to leave the organization with only the loss of one eye. He wears sunglasses so that his missing eye is concealed. When Eleanor Wish was hired by the Casino she met Yee and they eventually became lovers.
On Saturday 12 September 2009, Yee accompanied Wish to meet Harry Bosch at the Hong Kong airport to look for the missing Madeline Bosch. The three rode in Yee's black Mercedes. Yee obtained (illegally) a gun for Bosch. They found the hotel on Nathan Road where Madeline had been staying, but she was already gone. Yee became separated from Bosch and Wish. During that time Wish was shot by two would-be robbers and the robbers were shot by Bosch. Yee could have backed out at that point, but he continued to work with Bosch out of loyalty to Wish and Madeline.
Yee and Bosch went to the apartment of Peng Qingcai where they found Peng, his sister and their mother murdered. They also found the memory card from Madeline's phone with one potentially useful number on it. Believing that this is a number for the kidnappers, Yee sends text messages to the number to set up a meeting. This leads them to Northstar Seafood and Shipping where they found a boat used for human trafficking. Two men were shot and killed by Bosch. Yee and Bosch found Madeline in the trunk of a car. Yee delivered them to the airport so they could escape Hong Kong and get back to the U.S.
It is not entirely clear what happened to Yee afterwards. He was certainly interrogated by Hong Kong police in connection with the five deaths that occurred while searching for Madeline, but the ultimate outcome is not known.