After accepting the case, head to K-Bar in Central and talk to Ilyana, then fast-talk the next man for information. Afterwards leave K-Bar from the rear exit and reach the apartment for clues. When you had done searching, call Teng for further information.
Head towards the gambling den. Once pass the doorman and the hostess for the high stake table, start playing poker with Yar Kwai Lai. For the fourth game, try to lose the last hand on purpose to pass him an offer of a girl that you can trace in the next lead. However, if you happen to win, fast talk Yar Kwai Lai into buying the girl instead.
After meeting Ilyana and the smuggler, quickly take a photo of the two on the boat, then chase through the checkpoints on the bike. At the final checkpoint you'll need to grab a boat and head towards the tunnel outlet where the two are last detected. Head inside, take out the thugs and pick the lock on the cage to complete the case.