Edward Markham operates a shop called Markham's Used Books, which specializes in rare and collectable books. He is a long time acquaintance of Peter Bishop.
Next, he helped locate the buyer of the books that were sold to him years earlier by Peter. The books contained critical information related to Robert Bishop, Walter's father and are treasured by him. ("Jacksonville")
In the alternate timeline, Peter and Olivia return to ask him about a certain symbol but he has no idea who they are. He tells them about the symbol and David Robert Jones's apparent goals for the guided mutation of humanity. ("Nothing As It Seems")
In 2036, he lives alone in an apartment with an ambered Olivia Dunham. He pines for her and plans to wake her up eventually, but Walter, Peter, Astrid and Henrietta show up to rescue her. He appears to have become even crazier in the future, tries to keep his rights and stays away from Loyalists and Observers alike. ("Transilience Thought Unifier Model-11")