Agent Olivia Dunham works as an FBI liaison officer who mediates between different departments of the FBI and other law officials. When her lover, Agent John Scott is infected with an unknown pathogen, Olivia goes above and beyond to save him. She tracks down Peter Bishop who helps get Walter Bishop out of the institute. This work makes her visible to the FBI who offer her a job working in Broyes department on the Fringe cases. Olivia agrees, and joins Peter and Walter trying to assist in the investigation.

Son of Doctor Walter Bishop, Peter is reluctantly brought back from Iraq to act as guardian to his institutionalised father, who is needed to assist the FBI with their investigation into the unexplained phenomenon. Peter, also with a brilliant mind, has a lot of issues with his father, and blames his father for the break up of his family. When working with his father on the Fringe case, Peter realises how brilliant his father is, and decides to try again, and decides to stay and continue working with the FBI on the Fringe investigation.

Doctor Walter Bishop has been in a mental institution for 17 years after an accident at his laboratory left 1 man dead. Walter was working with military on "Fringe Science", the outer limits of "regular" science, often called pseudo science, which includes invisibility, cell reanimation, and neurological advancement to name but a few. After meeting Dr Bishop, it's clear he is a brilliant but unorthodox scientist.

We meet Agent Broyes at the plane incident of episode 1. He clearly is a big authority in the FBI and has a big issue with Agent Dunham. It turns out Olivia Dunham, while working as an Air force investigator, helped put away a friend of Broyes who was arrested for rape. He blames Olivia, telling her she ruined a 30 year career based on a "lapse in judgement". As Olivia proves her worth during the investigation, Broyes seemingly has a new appreciation for Olivia and offers her a job in his department.