John Pendleton is a wealthy, reclusive resident of Beldingsville living alone in a large mansion. His bitterness and isolation originate from a deep romantic disappointment involving Jennie Harrington, Pollyanna's mother, whom he loved. When Jennie chose to marry Reverend John Whittier instead, a heartbroken Pendleton withdrew from society, living without companionship or household staff, taking meals at a local hotel and collecting artifacts during foreign travels.

He initially resists Pollyanna, ignoring her greetings and maintaining a gruff exterior. After Pendleton suffers a leg injury in the woods, Pollyanna discovers him and summons help, including Dr. Chilton. During his recovery, Pollyanna visits regularly. Her conversations gradually soften his demeanor. Her resemblance to Jennie and persistent optimism remind him of his lost love, but her presence also begins to heal his emotional wounds. He eventually confides in Pollyanna about his past relationship with Jennie, revealing the source of his loneliness.

Seeking to fill the void, Pendleton asks Pollyanna to live with him as a surrogate daughter. Loyal to Aunt Polly, Pollyanna declines but suggests he adopt Jimmy Bean, an orphaned boy she befriended. Pendleton agrees, providing Jimmy with a home and gaining a newfound sense of familial purpose. This act marks a pivotal shift from isolation to active caregiving, alleviating his loneliness.

Following an accident that leaves Pollyanna unable to walk, Pendleton visits her bedside. He reveals his earlier adoption offer to Aunt Polly. Their shared concern for Pollyanna facilitates a reconciliation, helping mend long-standing tensions rooted in town gossip about their past romantic entanglements. His ongoing involvement with Jimmy Bean and support for Pollyanna during her recovery cement his transformation into a more integrated and compassionate community member.