Steven Moffat always leaves 'Sherlock' and 'Doctor Who' "secrets" lying around.
The writer, who pens the scripts for both the detective series and science fiction saga, admitted while plans are put in place to keep plans under wraps, even he leaves it to chance.
Fans have been speculating how Sherlock Holmes, played by Benedict Cumberbatch, faked his own death at the end of the show's second series, and Steven has faced a battle to keep everyone in the dark while filming the new episodes.
He told The Sun newspaper's TV Magazine: "We had crash barriers, behind which stood ranks of solemn women staring at what we were doing.
"All we could do was ask people: 'Please don't give it away'. That said, I'm endlessly leaving around my bag of 'Doctor Who' and 'Sherlock' secrets."
While Steven has a lot of work for both shows - and 'Sherlock' stars Benedict and Martin Freeman, who plays Doctor Watson, have huge film careers - he is keen to bring it back for a fourth series once its current run of three 90-minute episodes comes to an end.
He said: We are entering into that negotiation. Apart from the fact we have two of the biggest British film stars in our show, the rest of us are occupied one way or another ... But this can be worked out if everyone wants to do it. And everyone wants to do it."