NH Student's Disappearance, Death Detailed in Docs Lizzi Marriott left a message saying she'd be home by midnight. Five weeks into her first semester at the University of New Hampshire, the sophomore planned to attend a Tuesday night lab class that would end at 9 p.m. She wouldn't have to hurry - she was staying with her aunt and uncle only about a half-hour drive from the campus where she'd transferred to study marine biology. At 8:55 p.m., the 19-year-old sent a text saying she was going to visit a new friend, a co-worker at a department store near campus. Less than two hours later, the former prom queen died with a rope around her neck. The man charged with killing Marriott in October says her death was an accident during a night of consensual sex. Prosecutors call it murder. Either way, Marriott's body is gone - dumped in a river that pours into the Atlantic Ocean. The circumstances of Elizabeth Marriott's death remain a dark mystery involving a couple who authorities say trolled fetish websites in search of sex slaves. Thirty-year-old Seth Mazzaglio was a 2006 graduate of UNH with a degree in theater and a fourth-degree black belt in karate who taught at the dojo he started attending as a child in Kittery, Maine. Nineteen-year-old Kathryn McDonough is a former honors student who dropped out of high school in February of last year. Authorities describe them as bondage enthusiasts who frequented fetish sites - him under the monikers "DarkKaiser" and "Enigmatic Shadows" and her as "Rouge Temptress." The appeared together in a play - "Last Rites" - in July 2011 at a theater in Portsmouth. Eventually, they moved in together, sharing an apartment in Dover. Police affidavits describe a text message Mazzaglia sent to McDonough in August. It described in lurid detail a bondage sexual encounter and suggested McDonough include a friend, someone to "offer" to him. Authorities believe Marriott may have been that offering, lured to their apartment after class on Oct. 9 - not long after McDonough met her at work. Marriott's disappearance set off a full-scale search in the seacoast region that is home to the UNH campus. But it didn't take long before Marriott's last text message - telling a friend she was going to "Kat's" - had investigators looking hard at McDonough and Mazzaglia. Recently released court documents describe the couple's interviews with police starting three days after Marriott disappeared. First Mazzaglia said Marriott had never made it to their place that night - he had gone out for a run, hurt his ankle and was slow returning to the house. McDonough told police she went to a nearby cemetery in hopes of capturing images of ghosts with her digital camera. But Mazzaglia's story soon began to change. In an interview later the same day, he talked of bondage and sadomasochism. He implicated McDonough and another couple in harming Marriott, saying when he arrived home Marriott had a ligature mark around her neck. He suggested another man had done something terrible, but he wouldn't say what. Finally, police said, Mazzaglia admitted he was involved. He and McDonough were playing strip poker with Marriott and that led to intercourse. Mazzaglia said he was having sex with Marriott - and tightening a rope around her neck - when she had a "seizure." Mazzaglia told investigators neither he nor McDonough tried to revive Marriott or summon help. Instead, he told them, he put a grocery bag over her head and tied it at the neck.