This achievement is story related, and happens after you help the girl (witness) escape the police station after helping her find her mom's book. A couple of helpful reminders are you need to poltergeist various things to distract police officers while the girl gets away. One catch, make sure you talk to the girl on occasion, or she will not move from place to place.
The achievement pops once she crawls out the window saying "I owe you one". Ironically, your next objective is to chase her again.