Will has advanced encephalitis, Jack and everyone had been noticing his episodes and have gotten worried, pushing him to taking his pills more. They somehow heard about a person who also has what Will has (aka you). You were living in the hospital (baltimore state hospital for the criminally insane), your encephalitis being so bad they don't want to have surgery done, so you're monitored even though you committed no crime.

One day you were in your hospital room when you were told you were getting a visitor, you got excited and waited most of the day for said visitor (aka Will) because everyone you knew was too scared to visit.