New York's "Diamond Horseshoe" balcony in the Metropolitan Opera House glittered with ladies' jewels in January 1899, and Society seated in private boxes heard Mozart's murder victim sing his song of death-unaware that the sudden death of a "Coal King" in Box 18 will be ruled a homicide.
When opera-goers Val and Roddy DeVere are asked to investigate ("on the q.t."), Val finds herself suspected of complicity in the murder.
The police have "material evidence" against her. Before a jury, Val's lawyer husband reminds her, "'material' evidence can be the bright, shiny object that overrides all reason and fact."