Gilgo Beach serial killer Rex Heuermann’s ex-wife sleeps in the basement where he killed and dismembered his victims – leaving her “haunted by dreams” every night, she revealed in a documentary episode airing Thursday.

Asa Ellerup moved into the now-gutted kill room in their Long Island home after her psycho husband confessed to her that he’d slaughtered seven of his eight victims, she told the fourth installment of the Peacock doc “The Gilgo Beach Killer: House of Secrets,” produced in partnership with The Post.

“The brutal truth is that Rex Heuermann said he dismembered the bodies in this room,” she said in an interview in the creepy space.

“That is the brutal truth. Now there’s me. I am in this room. And I am here because I do feel spiritual.

“I’m trying to say spiritually in my own way that I am really sorry for what these victims went through.”

Ellerup, who finalized her divorce from Heuermann in March 2025, said she “completely gutted” his kill room – but cannot shake his sadistic crime spree.

“Every night when I go to sleep, I am haunted by dreams. Every night,” she said. 

“It will never go away. It will follow me for the rest of my life. There will never be any justice for anyone and there will never be any way to forget about this.”

In the episode,“Confession,” Ellerup said she still wants to know how Heuermann was able to hide his double life from her as she thought she knew the man she was with from 1993 and 2010.

“I want to get to know the other side of Rex. I want to know why Rex killed these women, what his triggers were,” she said.

“I am processing the information in a very different way because now I see evil in him.”

Heuermann admitted to killing eight women despite the fact he was only charged with seven murders.

Ellerup recalled visiting her ex in jail last summer, where he made that chilling confession.

“I understand that you are confessing to me on these murders — can you please tell me how many of these women did you kill?” Ellerup recalled.

He told her it was eight, one more than he’d been charged for, and that “all except one” were killed in his room in the basement of the Massapequa Park home where they raised their family.

Prosecutors have long claimed Ellerup didn’t know anything about Heuermann’s killing spree.

Long Island serial killer fears only arose in 2010 when the first of eleven sets of human remains were found along Ocean Parkway – near Gilgo Beach. Sets of human remains were discovered between 2010 and 2011.

Heuermann pleaded guilty to killing Amber Lynn Costello, 27, Megan Waterman, 22, Melissa Barthelemy, 24, and Maureen Brainard-Barnes, 25, who were famously known as the “Gilgo Four.”

He also copped to the murders of Valerie Mack, 24, Jessica Taylor, 20, and Sandra Costilla, 28, in the case that has gripped Long Island for three decades.

Heuermann also confessed to the murder of Karen Vergata, whose case hadn’t been linked to him.

He will not face charges in relation to Vergata’s murder, and will be sentenced on June 17.