For 17 years, the disappearance of Mike Williams haunted the close-knit community of Tallahassee, Florida.

The 31-year-old real estate appraiser vanished during a duck hunting trip on Lake Seminole in December 2000, leaving behind his wife Denise, their young daughter and countless unanswered questions.

Authorities initially suspected Mike had fallen from his boat, drowned and been eaten by alligators.

The truth emerged in 2017: Mike hadn't drowned that December morning -- he had been murdered, authorities said, the victim of a calculated plot between his wife Denise and his best friend Brian Winchester.

"Mr. & Mrs. Murder," a four-part ABC News Studios series, is streaming in its entirety on Hulu.

Courtesy Russell Grace via Plum Productions Ltd. - PHOTO: Mike and Denise Williams on their wedding day in 1994. They had been high school sweethearts before his disappearance in 2000.

On Dec. 16, 2000, Mike's wife Denise called Brian's then-spouse Kathy Thomas in a panic.

"Around noon, Denise calls me. And she says, 'Do you know where Brian is? Do you know where Mike is?'" Thomas recalled to ABC News.

Brian appeared at his in-laws' home later that afternoon. He told Kathy he'd gone hunting alone, she said. Meanwhile, search teams found Mike's abandoned boat and truck at Lake Seminole.

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From Lake Seminole's establishment in 1957 to the present time, just over 100 people have drowned in the lake. Of them, only Mike's body has never been recovered, according to authorities.

Cheryl Williams, Mike's mother, refused to accept that her son's body had been eaten by alligators, as law enforcement theorized. She stood on street corners with signs about her missing son, papered fliers along local roads, and placed newspaper ads begging for information.

Courtesy Plum Productions Ltd. - PHOTO: Lake Seminole, where Mike Williams supposedly drowned in 2000. His body was never found here - making him the only drowning victim never recovered from these waters

Behind the scenes, a dark story was unfolding. Brian and Denise, Mike's wife, had been carrying on a secret affair since 1997. Just six months before his disappearance, Mike had purchased a $1.75 million life insurance policy -- sold to him by Brian.

The case finally broke open in 2016 when Brian, by then married to Denise, was arrested for kidnapping her at gunpoint as their marriage deteriorated.

Facing serious prison time, Brian made a deal with prosecutors: immunity in Mike's death in exchange for revealing what really happened. In his confession, Brian described pushing Mike from his boat and shooting him after he managed to swim to a stump and hold on.

"He was panicking and I was panicking," Brian testified. "None of this was going like I thought it was gonna go."

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Brian then directed authorities to Mike's body at Carr Lake, an hour away from Lake Seminole, where it had remained hidden for nearly two decades.

"We were Bonnie and Clyde," Brian testified about his relationship with Denise. "We were partners in crime."

Courtesy Plum Productions Ltd. - PHOTO: Kathy Thomas, Brian Winchester's ex-wife, helped investigators break the case by recording a crucial conversation with Denise Williams in 2018.

In December 2018, a jury found Denise guilty of conspiracy to commit murder and accessory after the fact. She was sentenced to life in prison. Though an appeals court later overturned her murder conviction, her conspiracy conviction stood.

"Nobody's officially charged with his murder," Scott Dungey, Mike's best friend, told ABC News. "That was the only way. They would never have got the body, and Denise would still be out running free."

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Today, Brian is serving a 20-year sentence for kidnapping Denise, while she serves 30 years for conspiracy in Mike's death. The case continues to haunt those involved.

"Anslee's father was murdered, and she was raised by the people who did it," Jennifer Winchester, Brian's sister, told ABC News about Mike and Denise's daughter.

To this day, no one has been convicted of Mike's murder.

"When I go to bed at night, and I try to go to sleep," Mike’s mother Cheryl said after the verdict. "I see Michael clinging to that stump in the lake and I hear him calling, 'Help, help.'"