A Ring of Endless Light by Madeleine L'Engle is the story of almost-sixteen-year-old Vicky who comes to Seven Bay Island for her annual summer visit. This time, instead of spending two weeks like usual, her family is staying for much longer since her grandfather is dying. With three different young men interested in her, Vicky is thrown into a whirlwind of emotion as she deals with relationships, life, and death.

The summer begins with tragedy as a dear family friend, the father of Vicky's friend Leo, dies trying to rescue a rich young man who is drowning. Vicky has her suspicions about this rich young man, and they are confirmed when Zachary, a young man who met her the previous summer, tells her that he was the rescued individual. He hadn't been drowning, though. He been trying to commit suicide. He tells Vicky that she is the only good thing his life, and she feels that it's important that he has a second chance.

Meanwhile, Leo talks to her about his father's death and his future plans. She feels that it's very important to be there for him as a friend. He wants to have more than friendship, but she's not ready to offer anything more.

Grandfather is very ill, but he isn't too ill to talk with his granddaughter. Vicky reads with him and tells him about her relationship with the young men, and he offers insight. He appreciates his granddaughter's gift for writing, and he cultivates it. He encourages her to write and meditate when she is confused.

The third young man in Vicky's life that summer is Adam. He is a friend of her brother, John, and he is a scientist who studies dolphins. Adam invites Vicky to work and introduces her to dolphins in the pen as well as dolphins in the wild. They are both delighted to discover that she has a special affinity with dolphins and can communicate with them easily, even without words.

Grandfather takes a downward turn and needs to have blood for transfusions. Vicky and Leo go to the mainland to get blood for him. While they are there, Vicky has her first experience with the emergency room. It horrifies her, especially when she sees a young girl that she thinks is going to die. The girl reminds her of her little brother.

Grandfather regains his strength after the transfusions, and Vicky finds out that the little girl lived through that night in the emergency room. She has a disease, but is released from the hospital in good spirits. The summer is filled with dates with a three young men, playing with the dolphins, and reading to and talking with Grandfather. All seems be going well then life takes a quick downward turn. Stress, illness, and death surround Vicky, plunging her into an impenetrable darkness. Thanks to her family's love, Adam's caring, and lessons from the dolphins, Vicky learns to see the light again.