E-mails and text messages trigger a mass gathering of students to perform a random task on a golf course. However, as the crowd disperses, the body of a high school student is found. The original message triggering the "flash mob" is traced to a high school senior whose father is a high-powered defense attorney. Meanwhile Horatio and Yelina investigate the death of a meth addict found in a dumpster outside where she buys the drugs.