The Time Lord faces unknown enemies while trying to discover more about his latest companion Clara (Jenna-Louise Coleman) in an all-new trailer for the second half of Doctor Who Season 7 . Watch as we get a rare glimpse of Doctor Who's fearful side. What has the good Doctor so shook? Tune in to the mid-season premiere "The Bells of St. John" on Saturday, March 30th on BBC America to find out.