This chapter will be available if Ethan wasn't arrested twice (in Fugitive and On the Loose). This trial is the simplest one in the game. Just walk in the room and head to the table surrounded by cameras and video screens. All you have to do is drink the vial of poison or leave the room.
If you drink the poison and you've completed all the other trials successfully, you'll get the whole address and will go straight to where Shaun is being held. If you've only completed three or four trials successfully, you'll have to piece together the information you have to determine where your son is. If you look at the piece of paper in you car with the writing on it, you'll see that you've worked out a few possible addresses that could fit the pattern of what you know. You'll enter the three locations on the GPS and you can choose one of them at any time. Your only other clue is the cell phone, which if you listen closely contains an audio clue. You should be able to hear gulls in the background as well as the sound of a foghorn, indicating the location is close to the water. There is only one spot on the map fitting that criterion.
If you pick the wrong location, you'll drive to a restaurant and realize you didn't choose correctly, and you won't get the chance to save your son. If you completed less than three trials successfully, you won't be able to figure it out at all, and will likewise have no chance to save your son.