Warning: this article contains details from the final episode.

The ending was never going to be straightforward - nothing ever was in the world of Tony Soprano. That is why millions of viewers around the world have been addicted to eight years of plot twists that finally came to an end last night.

In the final scene: a final question mark. Millions in America tuned in to see the finale of The Sopranos, the hit HBO series, but the fate of Mafia boss Tony Soprano remains a mystery.

A shadowy figure slipped into the diner where Tony, played by James Gandolfini, was eating onion rings, surrounded by his family. As the tension reached crescendo and the audience expected the sound of gunshots to bring The Sopranos to a bloody conclusion, the screen turned black, the viewers held their breath, and then the credits rolled for the last time.

After 86 episodes and 18 Emmy awards, some fans accused the programme’s producers of ducking out of a definitive conclusion. Michael Imperioli, who played Tony’s nephew Christopher Moltisanti, defended the ambiguous curtain call. “I think it's a great ending. It’s a good way to go out,” he said.

The cliffhanger has prompted speculation that the mob family may return on the big screen. Steven Van Zandt, who played Silvio Dante, said: “We’re not sure it’s ending.”

Arthur Nascarella, who played Carlo Gervasi, also remained evasive, asked if The Sopranos would be back he said: “Wait three years and get back to me.”

There was no such ambiguity in the demise of Phil Leotardo, a rival mob boss who had ordered Tony's murder. Phil was shot as he got out of his SUV at a petrol station. His wife leapt from the car in horror allowing the vehicle, with his grandchildren strapped in the back, to roll forward and crush his head with a sickening crunch.

The cast of the programme, which first aired in 1999 attended an after show party in Florida. “We’re all heartbroken. We could go on forever. Me and Edie Falco [who plays Carmela Soprano] wanna die on the set,” Tony Sirico said, wearing the trademark silver wings of his character Paulie.

Hundreds of fans gathered in the Satin Dolls strip club, the set of Tony’s Bada Bing bar, to watch the denouement. Out of respect, the dancers took an hour off and joined the customers in Lodi, New Jersey marking a moment of television history.

Not everybody was satisfied with the outcome. “It was a big dud,” said Joseph Manuella, 57, who was among about 200 fans watching the show at Satin Dolls.

“People were getting ready for the big bang, like maybe the whole family was going to get whacked in the restaurant. But it was like a fireworks show without the finale.”

The final episode may have ended in confusion, but it was full of classic Sopranos lines. Tony told his close friend Paulie that he could run his own crew, but when he refused the offer Tony replied: “I’m a little miffled".

Paulie told his boss he once had a vision at the strip club. “One time, at the Bing ... I saw the Virgin Mary,” he said. Tony replied just as loyal viewers would have expected: “Why didn’t you say anything. F*** strippers, we coulda had a shrine, sold holy water in gallon jugs. . .coulda made millions.”

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