It could be the ultimate twist ending to “Making a Murderer.”

A Wisconsin man, who is already in prison for a separate slaying, reportedly confessed to the killing of photographer Teresa Halbach in 2005 — the subject of a controversial Netflix documentary, a new report published Monday claims.

The admission could pave the way for convicted killer Steven Avery’s exoneration, the report said.

The director of upcoming true-crime series “Convicting a Murderer” — an unaffiliated follow-up to the cult Netflix show — told Newsweek the inmate confessed to murdering Halbach during a taped interview, which is now reportedly in the hands of Wisconsin authorities.

“We haven’t confirmed the legitimacy of the confession,” director Shawn Rech said.

“But seeing as it was given by a notable convicted murderer from Wisconsin, we feel responsible to deliver any and all possible evidence to law enforcement and legal teams.”

Wisconsin man Avery and his nephew Brendan Dassey have spent more than a decade behind bars for Halbach’s murder but maintain their innocence.

Avery, 57, is serving a life sentence without parole.

The story made headlines when “Making a Murderer” first aired in 2016 — the show’s creators charting the pair’s repeated unsuccessful attempts to clear their names.

“Convicting a Murderer” will look at the famous case through the eyes of prosecutors and is expected to be released in 2020, website Digital Spy reported.

The inmate cannot be named until authorities have the confession, Newsweek claimed.