William Tyrell

On 7News Spotlight Liam Bartlett delves into the latest twist in the unsolved disappearance of William Tyrell, hearing from his biological mother.

"Sadly, this is a case that, for too long, has captivated the Australian public in the worst way. Either in the hope of finding little William - or find the person or people responsible for his disappearance," Bartlett said.

"Hopefully this time the new development is not another false start - and we can be part of a discussion that may lead to a genuine solution."

The three-year-old sparked one of the biggest manhunts in living memory when he vanished outside his foster family's residence in Kendall on the state's north coast in September 2014.

The investigation that followed uncovered shocking revelations, exposed paedophile rings, flaws in the foster care system, and led to the demise of Australia's most senior homicide detective.

In the seven years since, NSW Police have publicly identified numerous persons of interest only to ultimately rule them out.

In the past fortnight, on what would have been William's 12th birthday, detectives claimed to have finally cracked the case, urging the state prosecutors to charge William's foster mother for allegedly covering up his accidental death. William's foster mother has denied any wrongdoing.

This Sunday, Liam Bartlett will be joined by a panel of leading criminal experts, including Mark Morri, News Corp's most senior crime reporter who bought to light the investigation into the foster mother, one of the country's most effective homicide detectives, Charlie Bezzina; and, investigative author Caroline Overington as they navigate through the labyrinth of twists and turns in the ongoing police investigation surrounding the baffling case.

This explosive event will examine critical new evidence, key allegations, and introduce startling revelations that could reshape the narrative surrounding William's disappearance.

And, in emotional and never-before-seen interview with William's biological mother, candid revelations will challenge long-held assumptions – including her concerns about William's foster family.