josh mankiewicz: but who? the detective hope russell douglas' widow, brenna douglas, might shed some light on that. but that night, when he told her the father of her two children had been murdered, the detective says he got a strange feeling. i never try to judge how people are going to react when i tell them things. but her response wasn't what i expected. as in not emotional enough? she wasn't shocked, at least not visually shocked. it was a bit matter of fact. and that did leave us, at least, wondering when we walked out of the house, yes. josh mankiewicz: and so brenna douglas, as the wives of murdered men often do, became a person of interest. the domestic situation seemed unsettled. they were separated. russell was living in an apartment in renton. according to brenna, they were trying to work it out-- talking about getting back together. josh mankiewicz: in fact, the new widow told the detective that her husband had spent the holidays with her and the kids. she said the last time she saw him was the mo

josh mankiewicz: he sees things other cops don't see? phenomenal. craig melvin (voiceover): they call

here's josh mankiewicz with "as night fell." >>> they seemed so incongruous.he soaring majesty of utah's mountains and the story of a beautiful woman struck down in her youth. it was a lot of things. tragic. crushing. stunning. but was it an accident? or a suicide? or a murder? police felt they knew. but as most cops will tell you, both the evidence and the jury have their own stories to tell. and the answer is not always so clear. certainly, that is true for this story. and quite possibly for the woman at its heart. her name, heidi wagner. >> as a baby, she was savored, everybody loved her. she could do no wrong. >> autumn was one of heidi's four sisters. >> she was just special. you know, she'd walk into the room and she's ready for that good time. >> reporter: heidi grew up with no fewer than seven older siblings. >> tell me about her growing up. >> she was a fun-loving girl. she was rather shy, though. so heidi seemed like an appropriate name. >> heidi's mom, janet. >> the family would get together. we were kind of loud and boisterous sometimes. she got ki