A dramatic year in American lotteries is ending with a bang — and one big, ongoing mystery.

A $348 million Mega Millions draw is slated for Friday, marking what could be the eighth biggest U.S. lottery prize of 2018.

That will come on the heels of a $298.3 million Powerball prize won by a single ticket buyer in New York City on Wednesday night. The lucky player, who purchased the ticket at a service station in Brooklyn, was not immediately identified by Thursday morning, officials said.

And then there's the biggest lottery mystery to date: Who won the $1.53 billion Mega Millions draw of Oct. 23?

The holder of that single winning ticket, purchased in Simpsonville, South Carolina, has until Friday, April 19, 2019, to step forward to claim his, her or their — if it was a group purchase — prize, South Carolina lottery spokeswoman Holli Armstrong said Friday.

If no one steps forward, then the money would be returned to the 44 states that play Mega Millions.

Each of the states would "get back what they put in," Armstrong said.

C.J. Patel, owner of the convenience store where the ticket was purchased, is eager for that winner to step forward. He would get a $50,000 bonus for selling that winning ticket, money he said he would share with employees and his church.

But if a billion-dollar winner does not step forward, he'll get nothing.

"I thought it may take a couple of weeks because it's a lot of money to manage, but not this prolonged, long time," Patel told NBC affiliate WYFF last week. "But maybe, could be, he's waiting for the new year."