When a corpse is discovered in the theater of Martha's latest show, Castle and Beckett's investigation reveals suprising details about the world of competitive a capella.

Cast: Nathan Fillion, Stana Katic, Susan Sullivan, Jon Huertas, Seamus Dever, Tamala Jones, Molly C. Quinn, Toks Olagundoye, John Billingsley, Corbin Bleu, Mark Famiglietti, Fiona Gubelmann, Joe Regalbuto, Jaquita Ta'le, Sonya Eddy