LIN is instructed to keep an eye on BOB. BOB discovers her. YAN is so clever that she claims LIN as her sister who is a gambler. LIN is following him instead of BOB. BOB suspects them and goes to play mahjong in LIN's house. the ICAC set up a house to convince BOB. BOB is taken in. At last BOB is hooked. He asks NAY and YAN to smuggle drugs for him and he promises to give each of them fifty thousand dollars. However the company transfers NAY to another route and LIN replaces her. They follow BOB's instruction. They wear the pins and go through the number 4 gate. MING is ready to arrest them. NAY learns that it is a trick. She rushes to stop MING. MING changes the plan and waits for another opportunity.