Harington narrated the funny yet endearing fan experience on "The Tonight Show Starring Jimmy Fallon".
"I was driving back from my parent's house, and I was driving too fast actually. I was being a bit naughty. I was going over the speed limit, and I feel the sirens go off behind me," the actor recalled.
"And he said, 'Look, there's two ways we can do this: You can either follow me back to the police station now and I book you in, or you can tell me whether you live in the next season.' "
So, "I looked at him, and went, 'I'm alive next season'," the star says. "He goes, 'On your way Lord Commander. Keep the speed down this far south of the Wall."
Aside from his parents, girlfriend, the cop and "a few people," no one including the other "Game of Thrones" cast really knew about Jon Snow's fate.
"Sophie Turner, bless her, wrote me a really long letter about how much she loved working with me - and I still got it. That made me chuckle," Harington said.