Delirium is narrated by an elderly, unnamed retired philologist living in a row house in Oslo. At the beginning he believes that he and his childhood friend Martin are the final survivors of a group of eight boys who grew up together around a maple tree in a courtyard at Sagene. The others have gradually died, and the narrator is obsessed with how short life appears when viewed from old age. Martin and he supposedly preserve their friendship through a strict routine: Martin texts him on Tuesday mornings, arrives around eleven, waits outside smoking, and the two take long walks through their neighbourhood. Their route carries them past Polish construction workers led by Zbigniew, around a duck pond where they sit on a bench in silence, past an old prison where they sometimes imagine that their delinquent childhood acquaintance Ove is waving from an upper window, and eventually to Ibrahim’s café. These walks are less about reaching somewhere than about keeping the remnants of their lives organised. Both men are old, physically diminished and surrounded by absences, but the narrator’s decline is more serious. After strokes and periods on a heart-lung machine, his memory has become unreliable. He forgets actions, mixes past and present, and finds notebooks written in his own handwriting that he cannot remember writing. His doctor gives him cognitive exercises intended to distinguish memories, fantasies and false conclusions, but the narrator is contemptuous of the process. He continually reflects on Montaigne, language, ageing, envy, bitterness, friendship, fear, death and the strange relationship between remembering something and inventing it.
The narrator also believes that his wife Marie is still living with him. He describes more than sixty years of marriage, her newspaper reading, the home office she has made in their daughter’s old bedroom, their small irritations and their deep companionship. Marie eventually goes on a trip to Italy with female friends, leaving him alone. He speaks to her as if she were simply temporarily away and occasionally seems to communicate with her. Meanwhile Martin confides a much more urgent problem. His second former wife, Isabel, has begun demanding possessions from their marriage even though they divorced decades earlier. Most importantly, she wants a large share of the value of an old wooden sailing vessel Martin owns, an early Colin Archer design that has unexpectedly become extremely valuable because of its historical importance. Martin has spent years restoring the boat and regards it almost as a child. Isabel’s signature is nevertheless on the original purchase contract, for reasons Martin cannot remember, and she demands three quarters of the money that a maritime foundation is prepared to pay. Martin hates her with a frightening intensity. He says that before they die they need to “clean up” the disorder of their lives. This idea of cleaning up becomes one of the book’s central motifs: possessions, relationships, memories and guilt all become forms of clutter that the old men want either to understand or remove.
As Martin and the narrator investigate Isabel’s past, an increasingly dark family history emerges. Isabel came from a socially elevated but troubled family. Her veterinarian father had collaborated with the Germans during the occupation, accumulated money, created a new identity and avoided the postwar reckoning before eventually taking his own life when his past caught up with him. Isabel’s older sister Marianne later developed a terminal brain tumour. Before dying, Marianne secretly summoned Martin to the hospital and told him about their father’s collaboration and the family’s deliberate concealment of it. She wanted to know whether Martin would become like the rest of them and help preserve the silence. Martin never told Isabel about the conversation. He and the narrator begin viewing the entire family as one in which property, shame, inheritance, lies and secrecy pass from one generation to another. Martin’s adopted daughter Margaret further complicates everything. Margaret is separating from her husband and needs financial help, but Isabel refuses to guarantee a new home for her and cruelly reveals that Margaret is adopted. Margaret consequently breaks with her mother and begins telling Martin that she has always known something was wrong in their relationship. Martin alternates between feeling that he has finally recovered his daughter and seeing her as an unnerving reproduction of Isabel.
