When Tricia Todd didn’t pick up her 2-year-old daughter Faith from her babysitter on April 27, 2016, her family knew something was wrong.
After completing dozens of interviews, combing through hours of surveillance footage and chasing several dead ends, investigators were finally able to determine why Faith had not been picked up by her mother that day: the 30-year-old nurse had been killed. But even as detectives uncovered the surprising truth of what happened to Tricia Todd, they were left with more questions.
“What did we do wrong? Who did we just make a deal with?” Martin County Sheriff’s Office Lieutenant Yesenia Carde recalled in an interview with “20/20” Co-Anchor Deborah Roberts.
Investigators spoke in a new “20/20” episode, airing Friday, May 3, at 9 p.m. ET on ABC and streaming the next day on Hulu, about how they were able to sift through an array of leads to finally secure a shocking confession from Tricia Todd’s murderer – and arranged a plea deal to locate her missing body.
“I just made a deal with the devil, and there's nothing I can do about it,” the State Attorney for Florida's 19th Judicial Circuit, Tom Bakkedahl, told “20/20.”
One month before that deal with her killer, Tricia Todd was living in Hobe Sound, Florida – a quiet town of around 1,300 residents on the east coast of the state, about 40 minutes north of Palm Beach.
The “tight-knit” Hobe Sound community didn’t “have violent crimes like we were dealing with in this case,” according to Martin County Sheriff’s Office Chief Deputy John Budensiek. He described a missing persons case like Todd’s as “unheard of” and her disappearance one that set the community “on edge.”
Additionally, Todd was one of Hobe Sound’s own. Growing up there with her seven brothers, Todd was well-known in her hometown.
“[Tricia] would keep up with the boys, whatever they're doing, she's doing,” Todd’s mother Rebecca Hasselbach told Roberts. “They're jumping on the trampoline. She's jumping on the trampoline. When she got bigger, they had motorcycles. She had a motorcycle. That was her.”
Todd attended Hobe Sound Christian Academy, where she met Steven Williams – a boy from West Palm Beach. Todd’s friend Marnie Ellis described Williams as “super funny" with “a big personality.” Todd and Williams began to date, both enrolled in the Air Force, and later married in a small, private ceremony in North Carolina.
From a young age, Todd knew she wanted to be a nurse, according to her mother. After completing her time with the Air Force, she attended nursing school, began work as a hospice nurse, and made several medical mission trips to Haiti, her brother Jonathan Todd told “20/20.”
Then Todd received exciting news – she was pregnant with a baby girl. She named her Faith.
“I could not believe how happy she was,” Ellis said. “That was the most important thing to her, along with becoming a nurse, was being a mom.”
After Faith’s birth, Todd’s friends said they began to see her marriage to Williams unravel, with Ellis one friend telling “20/20” that Todd was bothered by repeated infidelity. In 2015, the two separated and Todd moved herself and her daughter back to Hobe Sound. After ten years of marriage, a divorce was officially finalized a year later.
Todd began to build a new life in Hobe Sound. She moved in with one of her brothers in his home about 2 miles from the beach, a location her family said she took advantage of to make late night beach walks to think and pray. Williams, still living in North Carolina, paid child support and visited his daughter.
It was during one of these visits in April 2016 that Todd went missing.
MORE: Video 30-year-old mom vanishes from Florida, concerning family and communityFaith was staying with her father overnight at a property he had rented near Todd’s residence. Williams texted Todd, telling her Faith was having trouble sleeping and asked her to come over to help. In early conversations with investigators, Williams explained that Todd tended to Faith and then left the rental house around 2 a.m.
The next morning, Todd did not arrive to pick up her daughter. Williams said that after trying to reach her all morning, he left his daughter with her babysitter before heading back to North Carolina. By that evening, Todd still had not surfaced. Worried family members alerted police to her disappearance.
Police searched Todd’s home and car and found her car moved from its usual parking spot with her keys and purse inside. Inside her home, groceries had been left on her kitchen counter. Her wallet and phone were missing, but there were no further clues about her location.
Interviews with Todd's friends and family revealed an initial lead -- Todd may have had a new romantic interest who “she was convinced...she was supposed to be with,” Ellis told ABC News.
His name was Brent Vernon, a local performer and ventriloquist. Ellis said Todd was infatuated with Vernon, even buying a new dress for an upcoming performance in the hopes of sparking a romance. Detectives were hopeful that Todd might still show up at that performance, a week after she was reported missing, and police set up surveillance of the venue. But she never appeared.
Brent Vernon was ultimately cleared by investigators of having any involvement in Tricia Todd’s disappearance.
Meanwhile, Williams, who investigators at the time noted was “pleasant and cooperative," may have identified a new lead: his ex-wife's late-night walks on the beach. He told cops that she’d venture out on her own, without her phone or any way to protect herself, like pepper spray.
Jonathan Todd told ABC News that there were some early theories that his sister might have experienced an injury or been kidnapped while she was on such a walk.
“Time became of the essence,” Jonathan Todd recalled about the investigation. “They're doing ground searches, they're searching neighborhoods, they're searching areas where she might've walked.”
Police spoke with someone who they suspected may know more: a local pastor whom Todd had previously encountered and prayed with during her beach walks. In fact, investigators learned he was on the beach the night Todd went missing.
He was cleared, however, thanks to a unique alibi that cops confirmed through surveillance footage: he had been watching a nesting sea turtle lay eggs.
When no other strong leads emerged, investigators returned to Williams for a second time, hoping to uncover more information. A polygraph Williams took was inconclusive and an interview with his girlfriend yielded little new insight.
Detectives continued canvassing the neighborhood near Todd’s house and eventually found something interesting captured on surveillance footage: the grainy image of a figure walking down the street the night Todd went missing.
Equipped with this footage, and expedited by the fact that Williams now wanted to move his daughter from Hobe Sound to North Carolina, detectives from the Martin County Sheriff’s Office, including Lieutenant Carde, flew to North Carolina to confront Williams in person.
Finally, Williams claimed that he and Todd did have an argument at the rental home that resulted in him pushing Todd. He said she fell, hitting her head, and he panicked when he realized he would be blamed. At that point, he told investigators that he drove his unresponsive ex-wife to the side of a road and left her there with a granola bar and water.
Despite this admission, Carde said there still wasn’t enough evidence for investigators to formally charge Williams with murder. Knowing there was more to uncover, Carde and the other investigators convinced Williams to return with them to Florida to help them locate Todd’s body. Multiple attempts at driving Williams to different locations were unsuccessful as he repeatedly said he couldn’t remember where he left Todd.
“At the end of the day, I just wanted to give Tricia back to her family,” Carde said. “We just wanted him to show us where she was.”
Without proof that Todd was dead, police charged Williams with child neglect, for leaving Faith home alone the night in question, and brought him in for another interrogation, where he finally admitted that he killed Todd, alleging it had been an accident. He was subsequently charged with second-degree murder.
MORE: Video 30-year-old mom vanishes from Florida, concerning family and communityBut investigators still didn’t know the location of Todd’s body. Williams was offered a plea deal that would reduce the sentence from a potential death penalty case to 35 years in prison in return for locating his ex-wife’s remains.
“When he said we were going to need a hazmat team, our heart just sunk,” Carde said to “20/20.” Williams took investigators to Hungryland Preserve, where he buried Todd’s remains in a plastic tote box of acid.
“It was clearly premeditated,” Carde reflected. The discovery left prosecutors and investigators regretting their plea agreement with Williams.
Williams is serving the 35-year sentence civil authorities agreed to in the deal.
The Air Force declined to federally prosecute him for crimes committed off base while on active duty.
In a statement to "20/20," the Air Force said, "While the Air Force has jurisdiction over any DAF member for crimes committed while on Active Duty, if crimes occur off-base, then civil authorities can claim jurisdiction over the crime. Civil authorities claim jurisdiction in this case as it occurred off of the installation."
Faith, now 10, was adopted by and is living with Todd’s brother Jonathan and his family.
“We love telling Faith about who her mom was,” Jonathan Todd said. “[Tricia] was just authentic…so willing to give of herself for others…and we teach Faith about that.”
ABC News' Laura Dimon, Blue Browning, Stacey Newman, and Glenn Ruppel contributed to this report.