'Sherlock' season 4 spoilers: EP Steven Moffat talks of Holmes and John's relationship after big premiere twist

The bliss brought about by the arrival of Mary (Amanda Abbington) and John's (Martin Freeman) first-born did not last very long as the growing family scales down to just being two once again by the end of "Sherlock" season 4 premiere.

Unfortunately, Rosamund Mary Watson would have to grow up without her mother, as Mary decides to sacrifice herself in order to save Sherlock (Benedict Cumberbatch) from being shot. The sequence was agonizing and emotional with John left crying over the death of his love.

While Sherlock is delving into the mystery at hand, he and Mary come face to face with the master puppeteer of the episode, Vivian Norbury, who becomes the latest person to quote from "Appointment in Samarra." Busted in her actions and with no way of getting out of the situation scot-free, while the snazzy kicks her to the curb by reading her on, the ice-lolly-loving stenographer retaliated by firing a gun at him. Time then slowed and just when Sherlock was ready to accept his fate, Mary jumped in front of him, taking the bullet.

With Mary gone, coupled with the way she met her end, some sort of animosity between Sherlock and John can be expected, and showrunner Steven Moffat reveals that they are planning to build on that.

"We take that rift head-on in the remainder of the [season]. We don't ignore it," he admitted in an episodic post-mortem with Entertainment Weekly. "We don't skirt around it. We don't just get on with the story of the week — although there is a story of the week. There's a big villain to fight. But front and center are the consequence of Mary's death and Sherlock's culpability. He could have done better, it's his lifestyle that killed her in the end."

Moving forward, does that mean that "Sherlock" is getting bolder in terms of character deaths, especially with the ongoing season? Moffat would not drop a name but he hints that "anything can happen to anyone" except to Sherlock Holmes and Dr. Watson.

"Nobody's safe and consequences are everywhere and there's some emotionally grueling stuff coming. There's proper humor too. We showed episode 2 to some people and though it's the darkest one we've ever done there were still people laughing," the TV exec shared.

"Sherlock" season 4 continues this Sunday on BBC One with the episode titled "The Lying Detective."