John Nevins is a CIA agent who works at the U.S. Consulate in Naples.
When Bourne arrives at Naples after Marie is killed in India, his passport pops up on the CIA grid. Nevins comes into an interrogation room to question Bourne about his visit to Naples. He gets a phone call from Langley telling him that the Bourne he has in custody is an "agency priority target." He then attempts to subdue Bourne by pulling out his gun. However, Bourne stands up and knocks out both Nevins and the Italian guard in the interrogation room. He copies Nevins' SIM card to tap into his mobile phone and leaves the building, stealing a car. Nevins gets a call from Langley to check his status. He reports that Bourne got away and that there is no way to secure him. Bourne then takes the stolen car (supposedly Nevins'), and heads to Munich to find the last surviving Treadstone agent. John Nevins is never again mentioned in the series.