You start the chapter in a virtual piano lounge in ARI. You'll play the piano by performing a quicktime sequence, with each button press corresponding to a note. After playing, your virtual butler will talk to you for a little bit, after which you'll get down to work. You need another lead in your investigation and you have a new clue to analyze. Open up your clues and cycle to the video footage of the traffic in the street outside the park where Shaun was last seen. Analyze the tape, which adds the car clue to your options, then analyze the car to get the license of a suspect in the car's theft. Finally, analyze Jack Neville's driver's license.
When you exit ARI, you'll have another withdrawal attack. The triptocaine is on the bedside table, and you can either go get it and choose to throw it away, or go straight to the bathroom and get under the shower to avoid taking the drug. Your other option is to take the triptocaine and pass out on the bed.