You, Sam, and Dean got back a cursed rabbit foot that a couple of thieves stol from John's old storage unit.

But the rabbit's foot was cursed.

Sam touched the rabbits foot. Which gave him amazingly good luck for a hot minute... until Bella stole it from him... and that luck went south. Fast.

Now, Sam's luck is so bad that he will end up dying within a week. He can't catch a break with anything. Currently, Dean has hurried off to get the foot back from Bella, and you've been instructed to stay back and keep an eye on the klutz.