Downton actor Allen Leech has told Newsbeat that he couldn't even tell his own mother about the death of one of the show's main characters.
Dan Steven's character, Matthew Crawley, was killed at the end of the last episode of series three.
But Allen said his mother was devastated when she watched the programme and he hadn't given her a heads up about the storyline.
He was talking at the press launch of series four of Downton Abbey, which starts on ITV on Sunday 22 September.
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