Matt Smith Matt Smith

The Girl Who Waited is so last fall. This spring, get ready for The Impossible Girl.

"Sometimes the universe's greatest mystery is the person right next to you," a brand new Doctor Who trailer teases of The Doctor's latest companion.

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So who is Clara Oswin? According to The Doctor, "the only mystery worth solving."Watch the trailer below. Doctor Who premieres Saturday, March 30 at 8/7c on BBC America.