Complexity of illicit drug markets mirrors the complexity of illicit drug use itself. The intricacy of multiple interactions between individuals, the various time lines linked to different aspects of harm reduction, and contrasted social rationalities observed among field practitioners (prevention, law enforcement, harm reduction) contribute to the creation of complex and unpredictable systems. In order to explore this complexity, an Agent-Based Model (ABM) called SimDrug was designed. The prototype model includes users, dealers, wholesalers, outreach workers and police forces. The model is focused upon local drug market and the hot spots in Melbourne. The time span for the model is 4 years, and the team endeavoured to replicate the period of the Australian heroin drought. One interesting question to answer was whether the drought was an emergent phenomenon or caused by externalities. Preliminary results tend to provide comprehensive answers to the question and meaningful insights for further developments of the model.