A sixty-two-year-old delivery boy, Otis Amber, delivers six letters to people handpicked to live in a luxurious new apartment building called Sunset Towers. The man who signed the letters, Barney Northrup, doesn’t actually exist. Despite that fact, a man calling himself Barney Northrup shows all the prospective tenants the apartments, and by the end of the day, he has rented them all. The new tenants come from different walks of life and include several families with children as well as single people. Included in the apartment community are the doorman, the in-house cleaning woman, and Otis, who makes many deliveries to the buildings.

Two months after the tenants move in, everyone except Sydelle Pulaski notices an unexpected occurrence: Smoke rises from the chimney of the nearby deserted Westing mansion. Sam Westing, who owns the Westing Paper Plant, disappeared thirteen years ago, though some people believe his corpse still lies in the house. Sandy, Sunset Towers’ doorman, tells Otis, Turtle Wexler, Theo Theodorakis, and Doug Hoo a scary story of two kids who went into the Westing house one year ago and ran out like they saw a ghost. Turtle, a junior-high-school student and budding businesswoman, offers to sneak into the house for money. In the eleven minutes she remains inside the house, she sees a waxy-looking man, believed to be Sam Westing, lying in his bed, seemingly dead.

News of Sam Westing’s death hits the newspaper. Westing was an industrialist who had built his own business and died a multimillionaire, alone—his adult daughter had drowned, and his wife had left him. Years ago, Westing had been in a serious car accident, and he had not been seen again until he showed up dead in his house. The following day, Otis delivers letters to sixteen of the tenants in Sunset Towers, which state that they are Westing’s heirs and invite them to the reading of his will.

The tenants assemble at Westing’s mansion. Grace Wexler, mother to Angela and Turtle, arrives first. James Hoo, owner of a fancy restaurant, comes with his son Doug, a high school track star. Theo and Chris Theodorakis also arrive; Theo is in high school, and Chris is his younger brother who suffers an unknown neurological condition. Also among Westing’s heirs are Dr. Denton Deere, Angela’s fiancé; Flora Baumbach, an older seamstress; Judge J. J. Ford, the first Black and female judge in the state who has past ties to Westing; and Sydelle, who has no apparent connection to Westing. Westing’s other heirs are Berthe Crow, the cleaning woman; Otis; and Sandy.

The reading of Westing’s will reveals that one of the heirs has taken Westing’s life. The heir who solves the mystery will inherit Westing’s millions. Heirs are grouped into two-person teams and receive clue words. However, the will instructs the heirs that it’s what they don’t have that matters. The teams all work to understand what their clues mean but with little success. Everyone is friendly with Sydelle because she took shorthand notes at the reading of the will. Judge Ford, partnering with Sandy, even hires a private investigator to find out information about the other heirs and their possible connections to Westing.

In the midst of the heirs working out the puzzle, a bomber strikes. The first bomb goes off in the coffee shop owned by Chris and Theo’s family when the heirs are meeting to discuss sharing clues. Later that evening, a second bomb explodes in Mr. Hoo’s restaurant, injuring Sydelle, who is taken to the hospital. Sandy and Judge Ford continue organizing facts about the heirs. They learn that Westing’s daughter Violet was childhood sweethearts with Mr. Theodorakis but committed suicide when her mother wanted her to marry a politician. Later, a third bomb goes off at Angela’s wedding shower, making a deep cut in her cheek and sending her to the hospital. Turtle figures out that Angela set the bombs herself.

As Judge Ford and Sandy keep studying their notes, they see a possible connection between Grace, who claims to be Westing’s niece, and Crow. They decide that Westing is not dead but wants revenge on his estranged wife, who must be Crow, for Violet’s suicide. Judge Ford and Sandy also have ties to Westing, however: Judge Ford grew up in the Westing mansion, where her parents worked, and Westing paid for her education; Sandy worked at the Westing Paper Plant but was fired.

When a fourth bomb goes off in the elevator in Sunset Towers, the heirs are summoned back to the Westing mansion. Now Westing’s lawyer asks each heir to provide the name of the person who took Westing’s life. No one is correct, but when they pool their clues together, they almost have all the words to the song “America, the Beautiful.” The missing word parts spell out Crow’s name. Suddenly, Sandy falls to the floor and dies. The lawyer returns and declares that they have just five minutes to give the right name and claim the millions. No one wants to name Crow as a murderer, but she gives her own name and is arrested.

Back at Sunset Towers, Turtle holds a fake trial. She’s been putting together ideas from the clues, the will, and the events. She says that Westing and Sandy are dead, but Crow did not kill them. Through questioning and explanations, she proves that Westing disguised himself as Sandy but that he also had three other identities, one of which she keeps a secret. Crow enters the room with Westing’s lawyer, having been declared innocent since Sandy died of a heart attack, and the lawyer hands over the final page of the will, which gives them all ownership of Sunset Towers and money to Crow. The next day, Turtle goes to the home of the Westing Paper Plant’s CEO, calls him Sandy, and announces that she won the game.

Turtle never tells anyone else about Sandy, whom she visits every week. Crow and Otis get married, and all the other tenants achieve their dreams. Turtle and Sandy remain friends for many years, and she sits with him at his deathbed. By then she has married Theo and become a successful, rich businesswoman. She inherits Sandy’s estate and becomes director of the paper company.