When you've walked the world for a while, you gather a collection of life experiences, each of which may teach you something: about yourself; about those around you; about existence itself. Those experiences give you a perspective on things, your "worldview", if you will, that shapes decisions yet to be made, influences your reactions to future events. It also has a profound impact on what you will tolerate, what you simply cannot, and what you simply move beyond. We as 21st-century humans have a journey of ninety to a hundred years at the very most, and our opinions can develop to a near-impenetrable state over that time. Imagine the fortress around the worldview of a traveler over two millennia old.

Twelve and Bill step back to 19th-century London to walk the frozen surface of the Thames. Oh, and punch Nazis.

As Sarah Dollard's sophomore contribution to the series, we delight in the continued chemistry between Capaldi and Mackie, find ourselves fascinated by a discussion over lives saved and taken, scream in triumph one uncharacteristic but fantastic punch, and get word from Dollard herself about that succinct but powerful "species" speech:

But before we start, take a moment to remember Pete, would you? We feel like we barely knew him.