The five-part series follows Barclay (Russell Tovey), a low-level UNIT staff member whose ordinary life becomes a world of terror when an ancient species rises from the sea. Barclay becomes humanity’s ambassador when the mysterious Salt (Gugu Mbatha-Raw) emergesfrom the Tank at a summit on the Thames.  

UNIT, led by Kate Lethbridge-Stewart (Jemma Redgrave), fights for control as humanity faces destruction.