The following version of this book was used to create the guide: Ward, Sophie. Love and Other Thought Experiments. Corsair, 2020.

Sophie Ward's Love and Other Thought Experiments is divided into 10 titled chapters, each prefaced by a philosophical thought experiment and a quote from the thinkers' writings. The following summary focuses on the novel's overarching plot points.

In Chapter 1, "An Ant," four years into Eliza and Rachel's relationship, their apartment becomes infested with ants. Eliza knows she must fix the problem to prove her love to Rachel. Rachel has been testing her ever since she expressed hesitancy to having a baby. One night, Rachel wakes up convinced an ant has entered her eye. Though skeptical, Eliza chooses to believe Rachel in order to preserve the relationship. Shortly thereafter, the couple's friend, Hal, acts as sperm donor, and the couple has Arthur. On his second birthday, Rachel insists she and Eliza discuss the ant. Eliza fears Rachel's obsession is a sign of mental instability. Rachel thinks Eliza's disbelief in the ant is a sign of her fading love. Not long later, Rachel is diagnosed with cancer. Rachel makes scrapbooks for Arthur. On his third birthday, the couple takes Arthur to Disneyland. While there, Eliza sees Mr. Kargin, the pest controller. His presence makes her believe in the significance of coincidences.

In Chapter 2, "Game Changer," while playing on the Grecian beach, Ali's friend loses his ball in the water. Wanting to impress his friends, Ali ventures into the sea. Once he gets to the ball, he realizes he must release it or he will drown. In one iteration of his life, Ali does not let go, and dies. In another, Damon rescues Ali. In a third iteration, Ali returns safely with the ball. In the latter version, Ali grows up to fall in love with his childhood friend. The summer she is meant to marry another man, Ali meets Elizabeth Pryce on the beach. Though Elizabeth is engaged to Nicholas, she and Ali have sex.

In Chapter 3, "Sunbed," Elizabeth and Nicholas Pryce attend a party. Throughout the night, Elizabeth is disgruntled. She cannot stop thinking about her daughter, Rachel. She does not approve of Rachel's public announcements about her sexuality. During the night, Elizabeth craves the attention of another attractive partygoer. She feels young again, thinking briefly of her youthful fling with Ali. When Rachel was born, she desperately hoped Nicholas did not notice she was not his daughter.

In Chapter 4, "Ameising," the ant narrates from the first person. One night, the ant smells death in Eliza and Rachel's bed. Unable to ignore it, she crawls into Rachel's eye and back into her head. There the ant discovers Rachel's tumor. She decides she must eat the tumor to keep Rachel alive. Over the years, she and Rachel grow closer, exchanging consciousnesses. The ant learns Rachel's stories through her thoughts and memories. When Arthur is a child, the ant realizes Arthur knows she exists. After Rachel's death, the ant crawls out of her body.

In Chapter 5, "Clementinum," Rachel stays home alone after Eliza and Arthur leave. Feeling unwell, she climbs into the bath with a book. Once in the water, she cannot focus. Her mind drifts between dreams and memories. In this liminal space, Rachel realizes that she owes her life to the ant, and that Ali is her real father. She dies shortly thereafter.

In Chapter 6, "The Goldilocks Zone," Greg picks Arthur up from school. He has assumed more parenting responsibility since Rachel's death. However, he still has trouble communicating with Arthur. He does not know how to respond when the boy asks where Rachel is. Their conversation leaves Arthur convinced Rachel is in outer space. Bothered by Greg's fairy tale, Hal and Eliza arrange a meeting. The parents argue over how to discuss death with Arthur. Greg thinks it is okay for Arthur to believe whatever he wants, because no one knows what really happens after death.

In Chapter 7, "Arthulysses," years in the future, Arthur pilots the spacecraft Spirit on a mission to the planet Deimos. Throughout the journey, Arthur continues losing himself in thought and memory. When his operating system, Zeus, notices Arthur's distraction, he insists on helping Arthur pilot. Arthur is glad he never had the system implanted; he feared having the same experience Rachel did with the ant. Then while docking the ship, Zeus announces their arrival back on Earth. Arthur is confused; his mission was supposed to last another year. In the hospital, Arthur becomes more disoriented. The world looks familiar, but feels wrong. When he tries escaping to find Eliza, he encounters Rachel.

In Chapter 8, "New to Myself," Rachel heads to the hospital to visit Arthur. Because the doctors said he was disoriented, she fears he might not recognize her. On her way there, Rachel thinks about her first love, Eliza, wondering what might have happened if they had stayed together. When she finally sees Arthur, she becomes confused and frightened. Though Arthur looks like Arthur, she knows he is not her son. In another iteration, a different Arthur lands in a different world. He exits the hospital in search of Rachel, only to find Eliza.

In Chapter 9, "Zeus," Arthur's operating system narrates from the first person point of view. He speaks to the reader and to Arthur, explaining that Arthur cannot exist without him. In fact, Arthur is just one in a litany of other Arthur simulations. Zeus intentionally placed the original Arthur in the wrong life to untangle the threads of time and space.

In Chapter 10, "Love," Arthur attempts adjusting to life with Rachel. He does not recognize her space nor her belongings. Worse, he now has an implant, which distracts him from and records his thoughts and interactions. With time, he realizes Rachel is not a monster. Together the two look through the old scrapbooks, and Arthur realizes he is connected to all versions of his life, past, present, and future.