The Providence Rehab Clinic is where Brian goes after he develops a cocaine addiction after becoming a drug-sniffing dog in "The Thin White Line".
When his behavior gets out of hand, the family decides to stage an intervention. Ultimately Brian agrees to enter rehab, forcing Peter and the family have to cancel the cruise they had planned until after Brian's treatment. Peter, disappointed at not being able to take a planned vacation and in awe of the fancy amenities at Brian's rehab rehab facility, decides to fake his own addiction in order to "vacation" at the detox clinic.
Before long, Peter's obnoxious behavior attracts the attention of the clinic's head doctor, and despite his initial attempts to ignore Peter, Brian gets sucked into Peter's antics, including causing 14 premature births at the nearby Teen Pregnancy Center. When the doctor claims that Peter is the "X Factor" responsible for driving Brian to his addiction, Brian indignantly exits rehab with Peter.