The co-creator and writer of BBC One's Sherlock has told Newsbeat that it's getting harder to persuade Benedict Cumberbatch to do the show.
Steven Moffat says it's because Benedict and Martin Freeman - who plays Watson - don't need it.
They both have successful movie careers which means their schedules are packed.
"They don't need Sherlock anymore. So we have to persuade them to do it - which is fair enough," he says.
Speaking at the BAFTA Television Awards nominees party in London last night Steven Moffat says he was surprised they signed up to a fourth series.
"They are very serious about it, they do love it very much," he says.
"I didn't think we actually thought we'd get a fourth series out of them."
But he revealed this year's Christmas special has already been recorded and series four is expected at some point in the future - when it's been filmed.
Steven Moffat also writes and produces Doctor Who and says it's usual to have to persuade actors to do shows.
READ MORE HERE: http://www.bbc.co.uk/newsbeat/article/32426270/sherlock-writer-says-benedict-cumberbatch-doesnt-need-the-show-now