SUK-FAN is attacked by birds and she is sent to the hospital for treatment. KIM-HANG leaves the hospital after recovering from an operation. He wants YIP TING to stay by his side and he lies to her that EDMOND is the one who killed her father. ATF tries to find out if the death of birds is related to biochemical attack and a poison gas factory is discovered. Somebody has stolen poisonous thallium from the research institute of university. The person involved in the case is YAT-KA's old classmate and she goes to the research institute alone for investigation but she is trapped in a fire. ATF assigns staff to visit the thallium expert Professor WONG. Professor WONG is a friend of YIP TING's father and YIP TING visits him to find out the truth behind her father's death. After investigation, ATF discovers that Professor WONG's assistant is involved in the case……