What happened to Lucille Butterworth?

It's been a long and deeply painful wait for action and answers to one of Australia's most baffling and enduring mysteries: what happened to model and bride-to-be Lucille Butterworth?

Her heartbroken partner and loving brothers are hoping today's sophisticated, thorough and dedicated police work will overcome the appallingly sloppy and inept police work of the past that saw Lucille dismissed as a runaway, compelling leads left unpursued and vital clues ignored.

In this powerful and revealing investigation Sunday Night's Mike Willesee follows the trails ignored or rejected by Tasmanian police after Lucille went missing from a bus stop outside Hobart in 1969.

Sunday Night has gathered new information and new accounts from key characters - including some who haven't spoken publicly before - that gives compelling perspective on this coldest of cases.

As a major coronial investigation of the case probes the errors of the past and identifies a key person of interest, Lucille's family and friends are hoping that finally their agony will end, her body will be found and her killer brought to justice.

Sunday Night airs on Seven, Sunday October 25, at 7PM