As she continues her search for a mentor, Diana meets wealthy alchemist Mary Sidney. London's vampire ruler demands fealty from Diana and Matthew as he is unnerved by their sudden arrival in the City.

Matthew and Diana arrive in France on their journey to face Philippe. Elsewhere, Louisa and Kit cut a swathe through London.

Philippe makes a troubling discovery, provoking a conflict with Matthew. Ysabeau, Em and Sarah start to look for a message.