I really enjoyed this book! The Heretic's Mark is the fourth book in the Jackdaw series I believe. The Saracen's Mark was the third book which was incredibly engrossing, I think I prefer Saracen's Mark over Heretic's Mark but I still definitely like both books. This book is set in London in 1594 where treason and rumours permeate the Queen's Court. Nicholas Shelby, a doctor with unorthodox methods, is accused of associating with Robert Cecil, a spy. Nicolas and his wife, Bianca flee for their lives to Padua. They follow an ancient pilgrimage route, meeting a strange, religious woman named Hella. Hella helps guide them to safety but has a vision which predicts an impending apocalypse. Bianca and Nicolas begin to question everything they know about their lives and the people around them which leads to a thrilling and fascinating story!