Overhearing fellow Mah Jongg player Olivia Schwimmer arguing with her husband, Paul, over the phone is the first time Sydney Bonner realizes the couple's "perfect marriage" is in trouble. A few days later, Paul is found dead just off the walking path around the town lake, his head bashed in. Fearing she'll be considered the most likely suspect, Olivia prevails upon Sydney and her three friends—Marianne, Katrina (Kat) and Micki—to find out who really killed him by using their connections.

Though none of the four has any professional investigative training, Olivia convinces them they have access to information law enforcement won't be able to discover. But in order for them to make progress, they must keep their efforts secret from their spouses, other friends and potential sources of information, they can only observe, listen and ask questions. Not easy for this group of take-charge retirees.

Meanwhile, life goes on. Sydney's husband, adjusting to retirement, plans a local follies that eventually draws in Marianne's husband and the rest of the gang. Chanteuse Kat learns she has a fan and possible suitor in the local sheriff. And Micki turns personal wardrobe consultant for Kat. All this and their weekly Mah Jongg game, too, as they close in on the killer.