At the beginning there is a young man struggling to stay afloat in a fast flowing sewer drain. Later investigation shows that he was dead before being placed in the sewer.
CSIs find out that the janitor's real name is Matthew Babajide and he is responsible for genocide in Rwanda. Babajide is a Yoruban last name. Yoruba live mostly in Nigeria, while the Rwandan conflict was between Tutsi and Hutu living on the other side of Africa.