In The Prince of Tides, Tom Wingo meets with Dr. Susan Lowenstein, a psychiatrist, in the hopes that together they will be able to help Tom's sister Savannah, who is suicidal. During his meetings with Dr. Lowenstein, Tom reveals his and Savannah's troubled childhood, which included poverty and abuse. In the end, these sessions not only end up being the key to helping Savannah, but also Tom, as he and Dr. Lowenstein work to heal old wounds and help Tom move forward towards forgiveness and a better way to live.
Tom travels to New York City to discuss his sister's problems with Dr. Susan Lowenstein, her psychiatrist. Starting in her childhood, Savannah experienced schizophrenic hallucinations involving bloody figures and dogs which tell her to kill herself. Savannah moves to New York and becomes an emerging writer of poetry, writing about her past as a way to escape from it. After many years, Savannah attempts suicide and nearly succeeds, the hallucinations still haunting her. In flashbacks which take up most of the novel, Tom relates incidents from his childhood to Lowenstein, who hopes that by finding out what pushed Savannah into her latest suicide attempt she and Tom can discover how to save her life.
We learn that Tom and his siblings were the offspring of an abusive father and uncaring mother. The father, Henry, a WWII bomber crewman who survived being shot down and managed to evade capture by the Nazis, thought that the best way to raise a family was by beating them, and did so regularly. He was a shrimp boat operator and, despite being successful at that profession, spent all of his money on frivolous business pursuits. One business attempt was a gas station that he advertised with a live tiger (that became the family pet, Caesar). These attempts leave the family in poverty. Their overly proud, status-hungry mother was only concerned for the family's public image, and would not let her children say a word about their father's abuse.
Eventually, Tom reveals the most traumatic event of their childhood, which ultimately caused the first of several of Savannah's suicide attempts. A man the children nickname "Callanwolde", who they first encounter in a wood next to their grandmother's home in Atlanta, escapes from prison with two other men and goes to the Wingos' home on Melrose Island, South Carolina. They rape Tom, Savannah (the twins were 18 years old), and Lila, their mother. Luke, who was working outside, comes to the house, sees the men through the window, and releases the family's pet tiger, Caesar, who kills the men raping Lila and Savannah; Tom kills the man who raped him. The mother and the children dispose of the men's bodies and she made them promise that they would never tell a soul about what happened.
After the revelation of the rape, Lowenstein feels that she is even closer to helping Savannah. Tom then tells the story of how their brother, Luke, died. Lila ends up divorcing Henry many years later, and marries Reese Newbury, a prominent landowner in the city of Colleton and former husband of a childhood rival, next to Melrose Island. Lila had gained the land in the settlement, and sells it to Reese. Reese sells all of the land in Colleton county and the Atomic Energy Commission begins the construction of production plants there. Luke, an ex-Navy SEAL who served in Vietnam, decides to fight for his land and the city, using guerrilla tactics to destroy bridges and building equipment, becoming a wanted man. He is tracked down by Savannah and Tom who try to persuade him to give up instead of being killed by the FBI. Luke is finally persuaded to surrender himself at a time and place of his choosing, but en route to the meeting, is shot and killed. Luke's death was the driving force behind Savannah's latest suicide attempt, and Lowenstein and Tom figure out that in order to save Savannah, she would have to write poetry about Luke's life the way she wrote about her childhood.
As the novel concludes, Savannah is making her recovery and Tom becomes closer to his wife and children. Henry, after being released from prison for drug trafficking, is confronted by Tom about his abuse, but does not remember ever hurting his family. Although Savannah and Tom can never completely forgive him for the damage that he did, they look forward to getting to know their father better, who acts like a changed man. By the end of the novel, they had not completely repaired their relationship with their mother, despite an earlier apologetic conversation between Lila and Tom.
Tom's meetings with Lowenstein also helped him better understand himself and save his marriage. Tom ended up as emotionally detached as his father and mother were, and because of this he never learned how to love his family. Sallie cheats on Tom, and the two nearly divorce. Tom falls in love with Lowenstein through the course of the novel, but realizes that he still loves Sallie. Lowenstein and Tom part ways after saving Savannah, and Tom returns to his family to become the father that he never was.