The sixteen Westing heirs, asked in Sam Westing's will to solve the mystery of who took his life. The players who are most aware of the truth behind this game are Judge Josie-Jo Ford and Turtle Wexler.
Sam Westing, whose will is a game to find a deserving heir for his fortune as well as to bring together relatives and other people whose life he influenced.
Sandy McSouthers dies in front of the heirs, and soon after is revealed by Turtle Wexler to be Sam Westing in disguise.
Turtle Wexler keeps to herself the entire truth, which is that the will asked the heirs to find "The Fourth": that is, the fourth disguise of Sam "Windy" Windkloppel, who turns out to be the newly-elected chairman of Westing Paper Products, Julian Eastman. Turtle wins the Westing game and becomes the secret heir of the Westing fortune.
Realtor Barney Northrup rents out the apartments of the newly-constructed Sunset Towers to a select group of tenants that includes the Wexler family (podiatrist Jake, wife Grace, daughters Angela and Turtle), the Theodorakis family (coffee shop owner George, wife Catherine, sons Theo and Christos), the Hoo family (restaurant owner James Shin, second wife Sun Lin, son Douglas), Judge Josie-Jo Ford, secretary Sydelle Pulaski, and dressmaker Flora Baumbach. The building not only has spaces to accommodate the businesses of Jake Wexler, George Theodorakis, and James Hoo, but also has a cleaning woman, Berthe Erica Crow, who also lives in the Towers, a doorman, Sandy McSouthers, and a delivery boy, Otis Amber. The tenants move into their new homes in September; on Halloween, smoke is seen rising from the Westing house, on a cliff that's within view of Sunset Towers. Rumors have it that Sam Westing, the rich industrialist who owns Westing Paper Products, has either returned to his old home or has been dead on the Oriental rug for a long time. On a dare, Turtle Wexler goes up to the Westing house where she discovers what she thinks is Sam Westing's body, dressed up like Uncle Sam.
The morning after, the newspaper reports Sam Westing dead. The inhabitants and workers at Sunset Towers --minus Barney Northrup, George Theodorakis and wife Catherine - receive letters inviting them to a reading of Westing's will the next day, as does Angela Wexler's fiancé D. Denton Deere. After the heirs gather at the appointed time, attorney E.J. Plum reads the testament, where Sam Westing reveals he has not died of natural causes and that one of the heirs present is guilty. The will asks his sixteen heirs to play a game to discover who took his life. To do this, the players are assigned into pairs: Jake Wexler and Madame Hoo, both of whom do not attend the reading and thus forfeit the money; Turtle Wexler and Flora Baumbach; Christos Theodorakis and D. Denton Deere; Alexander McSouthers and J.J. Ford; Grace Windsor Wexler and James Shin Hoo; Berthe Erica Crow and Otis Amber; and Sydelle Pulaski and Angela Wexler. Each of the pairs present are given a check for ten thousand dollars to encourage their participation and clue words written on pieces of Westing paper towel.
In the two weeks that follow, the pairs each go about this Westing game, interpreting their clues in very different ways as well as trying to find out the clues of other pairs. Along the way, new friendships and alliances are formed among the pairs. Grace Wexler becomes a de facto partner in James Hoo's restaurant and convinces him to revamp it as the sports-themed Hoo's on First. Turtle Wexler, long ignored by her mother, finds a new maternal figure in Flora Baumbach, who lost her daughter a year earlier. Through the intervention of Denton Deere, Chris Theodorakis, who suffers from a neurological illness that confines him to a wheelchair, takes a new medicine that improves his condition enough that an expensive operation becomes unnecessary. Jake Wexler and Madame Hoo strike up a friendship, as Jake teaches Sun Lin how to speak English. Otis Amber is the answer that two teams comes up with for Westing's murderer - Angela and Sydelle, as well as Theo and Doug. Theo is disgusted with his suspicions, however, when he discovers that Berthe Erica Crow and Otis Amber are busy running a soup kitchen in Skid Row. Neither Otis nor Crow seem focused on the game, as Crow is more concerned about Angela's welfare and tries to help her covertly.
Judge Josie-Jo Ford has a contact at the local newspaper to research Sam Westing and the Westing heirs; she also hires a private investigator who turns out to be one of the heirs. She finds out connections to Sam Westing, which varied in importance. James Hoo feels cheated by Sam Westing for stealing an invention of his, while Judge Ford's partner Sandy was fired from the Westing paper factory after trying to organize workers. As for the Judge herself, she grew up in the Westing home and her parents were its servants; she played chess with Sam Westing, who paid for her first-rate education. She suspects that Westing wanted a judge indebted to him and is determined to pay him back rather than be corrupted.
Judge Ford gives her half of the ten thousand dollar check to Sandy, and they piece together the main tragedy in Sam Westing's life: his daughter Violet was forced by his wife to give up her true love George Theodorakis so that she could marry a politician. (The wedding dress was made by Flora Baumbach.) Believing this fiancé to be crooked and worthless, Violet chose to kill herself rather than marry him. Mrs. Westing apparently went insane from this and disappeared, while Sam Westing later suffered great injuries during a car accident and had not been seen in public since. With Sandy's help, Judge Ford realizes that Berthe Erica Crow is the former Mrs. Westing and that she's the target of Sam's revenge. Further, Sandy thinks Otis Amber is really Sam Westing, which troubles Judge Ford as she believes she played right into Sam Westing's hand, as she did in her childhood games of chess.