This article contains spoilers for Season 8, Episode 6 of “Game of Thrones.”
The hero, Jon Snow, had been revealed as the grandson of a slain king. Daenerys Targaryen had a loyal army and the kingdom’s only dragon. Sansa Stark had proven her guile and toughness, while her younger sister, Arya, had saved the day at the Battle of Winterfell.
Plenty of these leading “Game of Thrones” characters had seemed to have a real shot at ruling Westeros when the series came to an end on Sunday. But the wagering on who would prevail, which took place in offshore and European betting markets in the weeks before the finale, didn’t give them much of a chance.
Instead, bettors were partial to Bran Stark, a.k.a. the Three-Eyed Raven, who had been an important, but lesser, character in the series.
Bran was no mere favorite: The final wagers for him to rule the kingdom were placed at 2-to-9 odds on one major offshore betting site, which implied that the probability he would prevail was almost 82 percent.
[Read our recap of the series finale.]
That made for an expensive bet. For every $45 risked, the profit would only be $10. It was the sort of wager to make only by those who are pretty certain they are right.
And right the bettors were: During the finale, Bran was appointed king by a council of other main characters, a “head-scratcher” outcome that flummoxed many fans.
Other heavily bet scenarios paid off as well. For example, at 1-to-3 odds, Jon had been a strong favorite to kill Daenerys in the final episode — even though he had been her lover (and was her nephew) and repeatedly professed loyalty to her as some of his allies expressed doubts.
The bettors were right on that one, too.
To professionals who make their money wagering, it seemed clear what had happened: Despite a tremendous effort by HBO to keep the ending a secret, key plot details must have leaked, and some bettors had inside information.
“You never see 2-to-9 odds — that really tells you something’s going on,” said Bill Krackomberger, a professional sports bettor based in Las Vegas.
Even if you did come across odds like that, he said, the measly payout would make for a bad gamble: “How can you bet on something like that, anyway? You’re getting pennies on the dollar.”
It’s hard to know for sure who might have leaked the details. Employees at television providers and streaming services in the more than 150 other countries that broadcast the show had a legitimate need to see episodes before airtime, and thus might have been able to make an informed wager. But they would have seen the episodes only about a day in advance, and bets on Bran to win had spiked well before that.
Some anonymous leakers used Reddit to provide details of episodes of the series before they were broadcast, including Bran’s ascension and Jon’s stabbing of Daenerys in the finale. One Redditor who got some key details right said their source was a relative who had worked on the show.
“Game of Thrones” inspired a robust betting market on offshore betting sites and in Europe, where some bookmakers said the volume of bets eclipsed all but one other television show in history, the hugely popular Eurovision Song Contest.
But there was no strictly legal way to wager on the show in the United States, partly because of concerns over leaks and inside information. Some bookmakers asked regulators for permission to offer bets, but were told no. And others in Britain and Ireland had suspended wagers in the final weeks, amid worries that inside information had spread.
To Mr. Krackomberger, the overseas betting frenzy recalled a famous moment in the annals of Las Vegas wagering.
In 1980, one of the city’s legendary bookmakers, Sonny Reizner, had offered odds on “Who shot J.R.?” before the answer was revealed on the hit CBS series “Dallas.”
But Nevada gaming regulators forced Mr. Reizner to cancel the bets and refund the money before the episode was broadcast, over worries that a lot of people already knew the answer. When the show aired, the culprit was revealed to be J.R. Ewing’s sister-in-law.
Unlike Bran, though, she had only been a 7-to-2 underdog in Mr. Reizner’s betting lines.
