Who does grace wexlerthink the killer is?

In the novel "The Westing Game" by Ellen Raskin, Grace Wexler suspects that the killer is Sam Westing, the wealthy owner of the mansion where the story takes place. She believes he is orchestrating the game to manipulate the heirs and reveal their true characters. However, her suspicion reflects her own self-interest and ambition rather than solid evidence. Ultimately, the story reveals deeper complexities and connections among the characters rather than a straightforward answer.