At the height of wedding season on Nantucket, Chief Ed Kapenash of the Nantucket Police Department receives a call from his deputy, Sergeant Dickson. Twenty-nine-year-old Merritt Monaco, in town to participate in a wedding, has been found drowned dead. Merritt’s body was discovered at dawn by the bride, Celeste Otis; Merritt was to be Celeste’s maid of honor. In light of Merritt’s death, the wedding has been cancelled. Dickson informs Kapenash that “the Greek,” or Detective Nicholas Diamantopoulos, is on his way to interrogate the guests at Summerland, the estate where the wedding was to take place between Celeste and Benjamin “Benji” Winbury, the younger son of the wealthy Garrison-Winbury family, Summerland’s owners. Chief Kapenash plans to join the Greek in his interrogation.

The timeline shifts to a day prior. Blond and immaculately dressed, Greer Garrison Winbury, Benji’s mother, drives to Nantucket shore to pick up Celeste’s parents. The couple has arrived by ferry from New York City to attend the wedding. As she drives, Greer contemplates the upcoming wedding. Celeste has left all the wedding planning to her, which Greer appreciates; Greer’s older son, Thomas, married Abby, oil tycoon Mr.