The Shell Seekers is a family saga stretching across three generations, recounting their relationships and the trials and tragedies that ensue. It is told from different perspectives, through flashbacks and shifting time periods.

After surviving a heart attack in 1980s Britain, Penelope Keeling looks back over her long life and her various relationships, from her bohemian childhood with an artist father in Cornwall, through her unhappy marriage to Ambrose, her great love for Richard who was lost to the war, and her three very different children: snobbish Nancy, selfish Noel and "special" Olivia.

The novel is set mainly in England, with much emphasis on the war years, although Penelope also visits Ibiza, where Olivia lives for a while with her lover.  When he dies, his teenage daughter Antonia comes to live with Penelope in London, where she has to make sense of her own relationship with the mysterious gardener Danus.

The book's title comes from a painting given to Penelope by her father. In later years, when the painting is found to be very valuable, the family argue over what should be done with it, and their true characters are exposed. Penelope must decide the best interests of the family; her dilemma is a battle of sentimentalism versus materialism. In trying to resolve it, Penelope is forced to confront the unsettled issues of the past so that she can make the best decision for her family.