Complete story — includes the ending
When a fringe event causes people to spontaneously combust, Walter determines that the deadly nanites behind the combustion were created by his old business partner William Bell. The team faces off with David Robert Jones and through use of Olivia's cortexiphan powers, defeat and kill him. Walter goes looking for William Bell and finds him in a warehouse where he is collecting the designer monsters he has been creating. Astrid is shot as she and Walter try to escape.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, Fringe season 4. HTML formatting and reference markers removed. · Content license