Get ready for Holmes and Watson to be tested to their limits in season four of Sherlock. That’s what Benedict Cumberbatch, Mark Gatiss and Steven Moffat teased in the press room at San Diego Comic Con.

“It’s very, very dark plot wise and things that evolve plot wise and psychologically that evolve because of the plot is enormous and sort of defining for the series,” Cumberbatch said. 

He went on to tell us that the script was shocking, very emotional and packed full of action.

Holmes will be dealing with his actions from the end of season three. Moffat explained how they softened Holmes in the beginning of season three. He was becoming more human. Moffat reminds us that becoming more human doesn’t make you nicer.

There was no way around it. Holmes logically saw that it was right to kill a bad man to save a good one.

“He wouldn’t have had a problem with that, he wouldn’t have an emotional difficulty with that,” Moffat said.

Toby Jones will be joining the cast as the darkest villain Sherlock has seen yet. Moffat said even though Cumberbatch looms over Jones, Jones still feels like a physical threat. 

We spoke with Cumberbatch one-on-one and exclusively with Gatiss and Moffat about what’s ahead for Sherlock in season four.

While this will be the darkest season yet, Cumberbatch said you can still expect the same humor and dynamics of the relationship between Watson and Holmes.

Later at the round tables, Cumberbatch said Watson and Holmes will be tested to their limits. 

He had nothing but praise for his co-star, Martin Freeman. He absolutely loves working with him and said: “He’s razor sharp. I don’t think I’ve met someone who’s as fast as him, as funny as him. He’s such a great actor so that just deepens every time.”

Because of the familiarity as friends and colleagues, Cumberbatch said the writers are able to throw anything at them and they’ll run with it. 

The actor is very excited about playing a darker side of Holmes. “It keeps us coming back for more. You don’t want to keep playing the same notes,” he said.

Gatiss teased a very exciting scene coming our way in season four. The cast always performs scenes for the crew before filming. This scene consisted of six or seven pages with a lot of the cast. After the scene was finished there was a silence and then crew erupted in applause.

Stay tuned for more updates on season four of Sherlock, coming in 2017.