Behind the scenes at "Downton Abbey"

"Sunday Morning" on the set of the PBS series "Downton Abbey," at Highclere Castle southwest of London.
CBS News

(CBS News) The hugely popular PBS series "Downtown Abbey" is now entering its third year. Many have dreamed of visiting that stately home, but our Martha Teichner has actually done it:

Oh boy, here we go: In Season Three of PBS' sudsy blockbuster "Downton Abbey," Shirley MacLaine arrives to take on Dame Maggie Smith.

Violet, Dowager Countess of Grantham (Maggie Smith): "I'm so looking forward to seeing your mother again. When I'm with her I'm reminded of the virtues of the English."
Matthew Crawley (Dan Stevens): "But isn't she American?"
Violet: "Exactly."

True fans can't wait for this battle of the acting legends. Never mind "Top Chef" - the knives are out and ever so sharp at Downton Abbey.

In case you've been under a rock for the last two years and have never heard of PBS' Emmy-winning hit, here's a quick primer.

Downton Abbey is the fictional home of Robert Crawley, the Earl of Grantham, and his American wife, Lady Cora. He's got the title; she's got the money.

One look at the class picture will tell you how many plot lines there are.

"Sunday Morning" on the set of the PBS series "Downton Abbey," at Highclere Castle southwest of London. CBS News

The series begins in 1912, has worked its way through WWI, and is now inching into the 1920s - years of major upheaval in British society as a whole, and for the aristocracy especially.

Season 3 spoiler coming up! The money - the lion's share of Cora's fortune - is gone!

"We knew that this series would to a certain extent be the charting of the downfall of this particular class," said Julian Fellowes, who created "Downton Abbey." "It would be their sidelining politically, their undermining financially."

Fellowes was flabbergasted by the worldwide audience response.

"No one is prepared for this extraordinary kind of whirlwind that took place, and if you expected that you'd be a fool," he said.

The show is seen in 170 countries. It's been nominated for 27 Emmys and has won nine. It's been a critical and ratings bonanza for PBS' "Masterpiece" - which nearly passed on it.

"I actually was a little hesitant, I can truthfully say," said "Masterpiece" executive producer Rebecca Eaton. Now, she is awfully glad she said yes.

"This is the cherry on top of the sundae, or the tea cake," Eaton said.

Speaking of confections - what could be sweeter than to be part of the first U.S. network television crew ever allowed on the set, in April, during the shooting of Season 3?