This week’s “Doctor Who” features some fantastic dialogue and relationship building between Bill and the Doctor—all on the ice of the Thames during the last Frost Fair. Plus, a giant fish that may or may not be an alien! Commentary on historical racism and classism! And at the end of the episode we get wild and speculatish about what’s knocking on the door of The Vault. Host Jason Snell with Erika Ensign and Lizbeth Myles.