Mark Seifert was a 31-year-old White man from the Machias area of Cattaraugus County, New York who vanished on February 13, 1984 after leaving a diner in Yorkshire Corners where he said he was heading to a business meeting. He left before 9:30 a.m. for a meeting arranged at an isolated spot on Pleasant Valley Road. That morning his Lincoln Continental was found later on Pleasant Valley Road engulfed in flames; the car contained no remains but investigators found pools of human blood, tissue and bone fragments nearby. The blood type matched Mark’s.

Several days before the meeting, Mark’s brother William had arranged for an acquaintance to contact Mark while posing as a secretary for Tri-State Developers and to invite him to that location. Fibers at the scene were later linked to material in William’s van. Prosecutors presented the physical and biological evidence, the circumstances of the arranged meeting, and William’s movements as proof of a fatal assault at the site.

William Seifert was convicted in 1987 of murdering his younger brother and sentenced to 20 years to life; the New York Appellate Division upheld the conviction in 1989. Mark’s remains have never been found; a family DNA profile was entered into forensic databases in 2018. Does anyone have information about where Mark’s remains might be located or who else knew about the Pleasant Valley Road meeting?