Arthur once lived on the streets, until he recovered from his low life and vices by been treated at the New Hope Foundation. He was stabbed on his back, which caused his death and at glance the crime scene indicated he felt to the water. However upon examination Dexter discovered he was killed elsewhere and then brought upon the water.
Deborah discovers Arthur Bleek was in fact an undercover Federal Agent, as a group of agents confiscate her work on the case and take her and the rest of Miami-Dade police off the case. Bleek was investigating Steve Gonzalez and was somehow discovered, which would be the reason of his death.