A new "Doctor Who" trailer released Monday offered a quick glimpse of 12th Doctor, Peter Capaldi, regenerating by the end of the new season, premiering April 15.

In the clip above, Capaldi's Doctor can be seen clutching the corner of a surface with his hand -- a hand that emits the telltale golden glow of a Time Lord in the stages of regeneration.

It was announced in January that Capaldi would not be reprising his role for a fourth season, but BBC has not yet named a replacement.

Capaldi's last episode will be the series' annual Christmas special, which airs December 25, 2017. No new Doctor has yet been set to fill the shoes of the show's first "Scottish" Doctor.

BBC announced on Friday that it had cast its first openly gay companion, Bill Potts (portrayed by Pearl Mackie).

"It shouldn't be a big deal in the 21st Century," Mackie told BBC. "It's about time isn't it? That representation is important, especially on a mainstream show. It's important to say people are gay, people are black -- there are also aliens in the world as well so watch out for them."

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