Phillotson leaves his post as schoolmaster in Marygreen to pursue a career as a scholar in Christminster. Little do we know at this point that he will eventually transform from honored mentor to romantic rival in young Jude's eyes.
Before he hits the road, he leaves his piano with Jude's aunt.
Like the decent schoolmaster that he is, Phillotson sends books to young Jude to help the boy with his studies. If he knew how things were going to go down with Jude's eventual arrival in Christminster, maybe he would have hung onto those books a little longer.
Years later, Phillotson meets Jude and Sue at his home/school outside of Christminster. He doesn't remember Jude at all.
As a favor to Jude, he takes on Sue as a teacher at the school. (We bet Jude regrets this favor, later.)
In a relatively short time, Phillotson falls in love with Sue and gets engaged to her. Sue wants to keep the engagement a secret—never a good sign.
Phillotson makes a surprise visit to Sue's training school in Melchester and discovers that she's been expelled for staying out all night without permission.
Phillotson marries Sue.
As the marriage falls apart, Phillotson agrees to give Sue the divorce she wants.
Years later, she returns and he remarries her, promising to not impose on her privacy.
As Sue offers to engage in a physical relationship with Phillotson, he tells her she does not have to do it. She goes ahead, even though she clearly doesn't want to, and that is the last we see of the old schoolmaster.