The blood on her Range Rover was the first clue that Jennifer Dulos’s disappearance last May would turn into something sinister.

The weeks that followed brought more revelations from the police, adding to a mystery that gripped the public.

Her blood was also discovered on the seat of a car her estranged husband had borrowed on the day she vanished. Nearly two dozen items with her DNA were found in garbage cans some 75 miles from her suburban Connecticut home. Then there was her ongoing acrimonious divorce case, in which Ms. Dulos, a mother of five, had said she worried she was in danger.

Yet even as each new detail made it more likely that Ms. Dulos had met a violent end, investigators could not find one key piece of evidence: her body.