IMPACT x Nightline: Tracy Anderson: Fitness, Fame and Hollywood

Former high school football star, Nick, and his girlfriend, Emily, were once happy, popular kids from well-to-do families. Now both heavily addicted to carfentanil, an opioid 10,000 times more potent than morphine.

Three addicted brothers have turned their childhood home into a hellish drug den where death is constantly at the door. As the brothers continue to struggle with the extreme abuse they suffered growing up, their mother sinks under the stress.

Jessica is now just a shadow of her former self--hopelessly addicted to fentanyl and meth. Her daughter has given a clear ultimatum: her grandchild or the drugs.

Nineteen-year-old Melissa went from being a happy-go-lucky high achiever to every parent's worst nightmare. Once a star athlete who spent her free time volunteering, Melissa now spends her days hungry for her next line of cocaine or sip of vodka.

Tim and Jessica, both 43, first met in the 6th grade but three years ago they reconnected on Facebook and embarked on a chaotic, drug-fueled romance that is destroying their lives.

When devoted animal rescuer, Shannon, develops a drug addiction, the one thing she can't seem to rescue is herself.

For Gabby and Patryk, it was love at first sight. So much so that 9-months later Gabby gave birth to their daughter. They also happen to be heavily addicted to drugs, and in the case of Patryk; the drug dealing lifestyle.

Now 31, Greg is addicted to a deadly mix of fentanyl and meth and living on the streets. Kept alive only by luck and the last vestige of a dream of becoming a professional musician.

Erika and Joey used meth together on their first date, beginning a drug-fueled romance that has wreaked havoc on their families.

A country boy at heart, Josh thrived in the great outdoors, but the grips of addiction now threaten his very survival.

Tommy and Melly, both 19, have had a troubled life for two people so young. In Tommy's teens, he witnessed the death of his beloved uncle due to fentanyl. Within months Tommy was using the same deadly drug to numb is pain.

Cassandra and Steven met in a rehabilitation center five and a half years ago. After leaving treatment, they moved in together and both quickly relapsed, spiraling deep into addiction.

Once a dedicated athlete, Garrett turned to fentanyl after a string of tragic losses. Shantell, who was in college and working as a barista, began using heroin after a nasty breakup and the death of her beloved grandmother.

Carlee, 26, and Cody, 28, became friends in middle school. Years later, their friendship turned to romance and crack cocaine and a life of crime.

Corinne, 30, met Joey, 36, while she was babysitting his 3 kids from an earlier relationship--it was love and drugs at first sight. On their second date they smoked meth together.

Once a loving mother to her five children, Danielle was the pride and joy of her family until a series of traumas from her past finally caught up with her.

Cody and Erin have a loving relationship, primarily founded on their addiction to drugs. Once a couple of bright kids with decent futures ahead of them, hard circumstances and family loss have derailed them.

After a sexual assault at university, Tristan spiraled into severe alcoholism. Now his liver is failing, and revolving trips to the emergency room have his family fearing for his life.