Xiao Tao, a "cheongsam beauty", is Sue's own sister. Xiao Tao Zi was taken away by Ding Rushan when he was a child, and escaped when he died, but because of amnesia, he didn't know his real name and family. Later, she was adopted by the Zhao family and named Zhao. After Sue returned to Shanghai, she applied to be Sue's maid, but she was actually a detective trained by Sue.

Xiao Tao, as Sue's detective assistant, lives with her. Sue says she is her maid, but Xiao Tao is actually her best friend and good partner at work. Xiao Tao Zi's investigation ability is outstanding, especially for some details that ordinary people can't feel. Sue likes Xiao Tao's cleverness very much.

After Ding Rushan was arrested, Su knew Xiao Tao's true identity. She is her own sister, and Xiao Tao regained her memory, so she and Sue recognized each other.

Xiao Tao and Su have a deep relationship. When Xiao Tao was framed, Sue found the evidence and washed away her grievances. Later, she realized that they were sisters. Sure enough, fate is wonderful.