狗是人类最好的朋友，我们很多人都与狗生活在一起。目前可以统计的狗的种类大约有400多种，那么狗究竟起源于何处呢？狗为何又是世界上种类最为丰富的哺乳动物呢？这个过程又是怎么发生的呢？本片试图与你一起解答这个谜团。

London, 1974. As Britain prepares for electrical blackouts to sweep across the country, trainee nurse Val arrives for her first day at the crumbling East London Royal Infirmary. With most of the patients and staff evacuated to another hospital, Val is forced to work the night shift, finding herself in a dark, near empty building. Within these walls lies a deadly secret, forcing Val to face both her own traumatic past and deepest fears.