CBS NEWS "48 HOURS MYSTERY" -- SATURDAY, APRIL 21

ERIC COPPLE -- PLAYED A KEY ROLE IN SOLVING THE CASE

A HALLOWEEN NIGHT DOUBLE HOMICIDE IN NAPA VALLEY WAS A CLASSIC WHODUNNIT UNTIL THE VICTIMS' LOVED ONES DISCOVERED THAT THE KILLER WAS AMONG THEM

"48 HOURS MYSTERY" -- SATURDAY, APRIL 21

Leslie Mazzara and Adriane Insogna were best friends and roommates living together with a third friend in Napa, Calif., a beautiful, almost idyllic community. On Halloween night 2004, Mazzara and Insogna were fatally stabbed by an intruder. The third roommate never saw the killer. The double-murder shocked the serene community and with no arrests made, the mystery eventually gained national attention. Investigators pursued every angle from a satanic cult to a disgruntled suitor, yet the murders remained unsolved. Could someone personally close to the victims avoid suspicion by simply hiding in plain sight? Correspondent Bill Lagattuta reports on the brutal wine country crimes with a strange twist. 48 HOURS MYSTERY: "Nightmare in Napa" will be broadcast Saturday, April 21 (10:00 --11:00 PM, ET/PT) on the CBS Television Network.

And who would be shocked most to hear a confession from a killer hiding in the girls' inner circle all along?

48 HOURS MYSTERY: "Nightmare in Napa," was produced by Paul LaRosa. The senior producer was Peter Schweitzer. Al Briganti is the executive editor. Susan Zirinsky is the executive producer.

Editors' Note: To purchase or read an excerpt from the new true-crime book version of Nightmare in Napa written by 48 HOURS MYSTERY producer Paul LaRosa, go to www.cbsnews.com/stories/2007/04/16/48hours/main2686638.shtml. 48 HOURS MYSTERY broadcasts are now available on iTunes.com.