Going about the events of her day, Clarissa reflects on the quality of her life in London and her marriage to Richard Dalloway. Her old suitor shows up unannounced and stirs up more feelings of the past, including memories of her erotic encounter with Sally Seton and of first meeting Richard. Meanwhile, Septimus and Lucrezia sit in the park. Lucrezia tries to remain calm as her husband demonstrates the disturbing signs of post-traumatic stress disorder.
Septimus is unable to face the possibility of living in one of Sir William Bradshaw’s psychiatric homes, so he commits suicide.
Clarissa’s party is underway and we learn that Sir William Bradshaw was once her doctor, too. She found him repulsive and thus feels deep empathy for Septimus, though she never knew him. The story ends with Clarissa feeling uplifted by Septimus’ great sacrifice, which she feels was made, in a sense, so she could once again see the beauty of life.