Iroh: I brought someone along who might be able to help us. (goes outside and presents bound-up Dai Li agent, Toph Earthbends to stand him up)
Dai Li Agent: Azula and Long Feng are planning a coup, they're going to overthrow the Earth King.
Sokka: My sister! Where are they keeping Katara?
Dai Li Agent: In the crystal catacombs of Old Ba Sing Se. Deep beneath the palace.