Horses were their passion, and the couple's romance had begun nine years earlier, with long rides into the countryside. By all appearances, the Franklins had it all - love, property worth millions, a thriving medical business, and a shared life on the farm.
But below the surface, things were starting to crumble. Sandra accused Peter of having affairs; Peter's medical practice was being investigated. The couple was arguing regularly, heading toward divorce. They argued over money, a million-dollar life insurance policy and how the property would be divided.
And then one hot August night in 2009, their argument began in the barn, amid the horses; it moved into the house, to the kitchen, then to the hallway. It turned physical. They each wielded knives, a small one and then a large one, as Sandra tells it.
Watch a sneak peek
Hear the couple's calls to 911
Who attacked who and why, well, it's hard to know. But at the end of it all, Peter Franklin lay in the grass behind the house clutching his bloody chest, and Sandra stood stunned in the hallway, trying to make sense of it all.
Self-defense, she says, there was nothing she could do. It was kill or be killed... or was it?
"48 Hours Mystery" correspondent Peter Van Sant has the rest of the story Saturday, Jan. 8 at 10/9c.
Produced by Alec Sirken