The Power of Love and Sacrifice
Harry Potter and the Prisoner of AzkabanThe theme of love as a protective force, exemplified by Lily's sacrifice and Harry's ability to conjure a Patronus.
increasing
Bearing strength in each event
decreasing
Lily's sacrifice

The Mother's Love
The Memory
Harry hears his mother's last moments every time a Dementor gets near. Her voice pleads with Voldemort to take her instead of Harry. This sacrifice is the reason Harry survived the Killing Curse.
The Power
Lily's love created a protective charm that saved Harry. This is a deep magic that Voldemort underestimated. It is the foundation of Harry's survival.
The Echo
Harry's experience of his mother's love gives him strength. It is a painful memory, but it is also the source of his ability to love and be loved. The theme of sacrificial love is central.
Harry's Patronus from love

The Stag Patronus
The Happy Memory
Harry's Patronus is a stag, the same form as his father's Animagus. He conjures it by thinking of the happy memory of being with his father, even though he never knew him. The love for his parents is the source of his power.
The Protection
The Patronus drives away the Dementors. It is a manifestation of positive emotions, the opposite of the Dementors' despair. Harry's ability to produce it shows his inner strength.
The Connection
Harry realizes that his father lives on through him. The Patronus is a symbol of the love that continues beyond death. This theme underscores the entire story.
The night Harry's parents died
Night of the Dementor attack