.
He lied to Mare about never having talked to her.
John is clearly the dominant one in their relationship.
Why did they burn the journals, and what is on the paper that Jess saves? After reading Malamud's call for action, Swartz used a running on to download the documents, using credentials belonging to a Sacramento library.
Which leads to our next possibility.
Maybe Mare never talks about his death because she feels responsible for keeping him around this group of people.