Christiane starts taking LSD in addition to abusing pills, and befriends a girl her age named Babsi. After a David Bowie concert, Christiane tries heroin for the first time. As she falls in love with Detlev, Christiane begins using heroin on a regular basis in order to be close to him, gradually becoming more and more dependent on the drug until she is a full-blown addict. After her 14th birthday, Christiane stops going home and spends more and more time at her cohorts' unkempt apartment; she is also drawn to Bahnhof Zoo, a large train and subway station notorious for the drug trafficking and prostitution that takes place in its underpasses and back alleys. Christiane also starts to prostitute herself, imitating Detlev, who sells sex favours to male clients on a regular basis in order to support his heroin addiction.