The captured agent was an ordinarily tough Dai Li agent who was captured by Iroh during the coup d'état in Ba Sing Se. He was taken to Team Avatar's home, where he revealed Katara's location of imprisonment, which was down in the Crystal Catacombs of Old Ba Sing Se. An identifiable trait of his was a medium-sized scar going from his right lower eye-socket toward the bottom of his right cheek.
When PrincessAzula proved true to her word on her taking charge of command of the Dai Li, she gathered the agents to organize them for the planned coup. While stating the consequences of any disloyalty or dishonesty, he was the only agent looking slightly bewildered at her statement.
He was later captured by Iroh, who was trying to get information in hopes of learning where Azula was holding Prince Zuko captive. He bound and gagged the agent and stripped him of his earth gloves and shoes, rendering him helpless. Iroh dragged him outside of Team Avatar's house in the Upper Ring, where Toph wedged him between two earth slabs, forcing him to stand. As soon as Iroh removed the gag, the agent revealed Azula and Long Feng's plan to overthrow the Earth King. Upon Sokka's demand to know where Katara was being kept, he told them that she was being held captive in the Crystal Catacombs of Old Ba Sing Se, deep beneath the Earth Kingdom Royal Palace. Iroh, Aang, Sokka, and Toph promptly left to help their loved ones, leaving the agent still bound by ropes and trapped by Toph's earthbending on the porch of the house.
The way that he was restrained by Toph in this episode was very similar to the way that she trapped one of Azula's Dai Li agents: by removing his rock gloves and squishing him within the space of a steel support beam, rendering him unable to bend.