Since the day after Thanksgiving, I’ve spent every waking moment investigating a murder that occurred nearly 35 years ago. During the holiday season of 1979, a woman named Grandma drunkenly stumbled out of her home and was allegedly struck by a Santa-driven sleigh. According to an eyewitness report, she got run over by a reindeer.

Grandma was a typical, cartoonish old lady. She wore an eccentric blue and silver wig. She liked to have a drink or two and was not a fan of taking her prescription medicine. According to those close to her, she would often deny her husband the right to watch TV or play cards with his buddies. Her favorite activity was nagging her family. By all accounts, she was pretty normal.

I first heard about the story as a kid. I never thought much about it until I actually sat down and listened to the testimony. Could it be true that jolly old St. Nick has a sinister side to him? Could his public displays of merriment in malls across the country simply be what psychologists like to call “superficial charm?” Could Santa be a sociopath? I had to find out.

I began looking into a possible motive.

Sure, Santa once had Grandma on his naughty list, but that same list includes millions of kids each year. Those that work under him say that Santa always roots for those bad kids to get on the nice list the following year. “He thinks of every child as his own, and he loves them all equally,” is how one elf describes his boss. If he harbored any real ill will towards Grandma, he certainly didn’t show any signs of it.

As for his alibi, Santa claims that he was at the Fredricks’ household, but he has no eyewitnesses to back this up. That might sound too convenient, but it should be noted that the Fredricks did receive their presents that year. If anyone had spotted him, he would’ve ditched their house, leaving them giftless. That’s just how Christmas works.

I wanted to reach out to the main eyewitness of the reported attack, but nowhere in his affidavit does he reveal his identity. All we really know about him is that he’s consistent in his recorded testimony. In fact, he never changes a single word in all of his accounts of the crime. It almost sounds too polished, like it’s been rehearsed.

I needed to see if there were any holes in his report that the police might have missed.

I’m not a detective, but I did rent a reindeer-powered sleigh to reenact the alleged crime to see if it was physically possible.

OK, so here’s the deal: I spoke with a Santa expert and he informed me that the big guy would have to visit, on average, 1,178 homes per second in order to meet his annual deadline. I wanted to see how long it would take a sleigh to go from an altitude of 40,000 feet to the eye level of an old woman. I performed this dive multiple times—clumsily, admittedly—but even on my best attempts it still took me a fraction of a second; almost an eternity in Santa’s world. And that’s not even putting in account that Grandma was clearly drunk and couldn’t have been a straight moving target. How could Santa have pulled off an attack on her and still accomplish his overwhelming workload under such a tight deadline? It doesn’t make sense.

And then there’s the evidence of the attack. The eyewitness claims that Grandma received a series of wounds, including “hoof prints on her forehead” and “Claus marks on her back.” Hoof prints are easy enough to fake, but what exactly are Claus marks? He has the hands of a human, not a Velociraptor. His story was unraveling very quickly.

Just as I was thinking this was closed-shut case and that I could move on with my life, I received an anonymous email that simply said, “CHECK THE NORAD REPORTS.”

I ended up reading the official report from that year and it led me down a strange trail of clues that ultimately brought me to the parking lot of a Bass Pro Shop, where I tried to hunt down an antiquated machine.

Next week on Serial, I investigate the mysterious malfunction of a Santa-tracking radar device that made St. Nick undetected for two very long seconds.