'Agents of S.H.I.E.L.D.' season 4 spoilers: Pilot episode features beginning of crossover with 'Doctor Strange'

The "Agents of S.H.I.E.L.D." season 4 premiere episode introduced a new supernatural element that begins to tie the Marvel TV series with the upcoming Marvel Cinematic Universe (MCU) film "Doctor Strange."

In the season 4 opener, May (Ming-Na Wen) and a group of Chinese smugglers were driven mad after coming in contact with a mysterious box that seemed to have unleashed or was guarded by a ghost-like apparition. The mist-filled box infected anyone who opened it, convincing them that everyone around them has transformed into monsters.

In a Q&A following the "Agents of S.H.I.E.L.D." season 4 premiere, co-creator Jed Whedon explained that the strange box is connected to Doctor Strange, the next addition to Marvel's long list of comic-based superheroes.

"...[W]e are introducing sort of a different supernatural element of the MCU to coincide with the release of 'Doctor Strange,'" he said. According to Whedon, while he can't reveal what the box contains, it is "along the lines" of the magical realm featured in the upcoming Marvel Cinematic Universe film.

While the show's previous tie-ins with MCU films, including "Captain America: The Winter Soldier" (2014) and "Avengers: Age of Ultron" (2015) have been more direct, its connection with the Benedict Cumberbatch-starrer will not be as obvious.

"The tie this year will feel more of a reflection of the movie, less an interweaving plot," Whedon recently told Entertainment Weekly. "As that movie hits the world, it comes at the right time in our show, and you will see some of those same ideas being explored."

According to "Agents of S.H.I.E.L.D." executive producer Maurissa Tancharoen, the questions the series are exploring in the episodes leading up to the "Doctor Strange" premiere will be reflected in the movie.

"Hopefully some of the questions that we're asking will be answered by it and then pose some new themes and ideas for us to explore," Whedon added in his interview with EW.

"Agents of S.H.I.E.L.D." season 4 airs Tuesdays at 10 p.m. EDT on ABC.