During a big sale at the local jewelry store, Samuel Bentley picks out a vintage sapphire ring that he knows Miriam Maxwell will adore. But she is shocked to recognize it as an heirloom piece of her mother's. When the gem falls out and is found to be phony, they find the art deco setting is etched with a name: Theo. While Samuel tries to track down the jeweler who has abruptly left town, they learn that other customers have also purchased jewelry set with fake stones. The mystery deepens when a man shows up seeking to claim an inheritance of costume jewelry which Miriam can't find. As she readies her late sister Ruthie's foursquare house for a Labor Day tour of homes, she and Samuel grow more curious. Why would Ruthie have sold such a precious family treasure? Who is Theo? Where is the missing costume jewelry? And did Miriam really know her sister at all? The investigation soon reveals that Ruthie was keeping a secret that is much bigger than Miriam could have imagined.