Peter Capaldi's Twelfth Doctor casts a long, ominous shadow over the first trailer for the "Doctor Who" spinoff, "Class."

If you thought the new series, set at Coal Hill Academy, would be all about peer pressure, dating and teen angst, think again. This first look, released to coincide with New York Comic Con, is downright foreboding, with the Doctor warning, "I can travel through space, I can travel through time, but I can't always be there when you need me."

"What will you do when the shadows come," he asks in voiceover," when y0u can't turn away from the darkness ahead? For Time has looked at your faces, and Time never forgets."

Created by “A Monster Calls” author Patrick Ness, "Class" centers on four students who have to grapple with the usual teen issues while also confronting the possible end of existence. It turns out that all of the time traveling within the “Who” universe has caused the walls of space and time to become thin — and now there’s something pressing in from the other side.

Debuting Oct. 22 on BBC3 and BBC America, "Class" stars Katherine Kelly, Greg Austin, Fady Elsayed, Sophie Hopkins and Vivian Oparah.