For reading the draft and checking for various errors, thanks to Jenny de Gex, Valentina Harris, Katie Bayer, Robin Stokoe, and also Anna South. My dearest friend from North Sydney Girls High School, Susan “Maysie” Lyons, in New York, encouraged me, checked the menu at the Tick Tock Diner, and suggested some very gentle sculpting. Fiona McIntosh at HarperCollins in London gave me confidence that this book was worth the trouble. Big thank-yous to Edward Bettison for the beautiful cover design, Ami Smithson, Claire Peters at Quadrille for the visuals of the puzzle texts, and Johnson Banks for getting us started with such flair. Late in the day, thanks to Professor Sebastian Lucas, of Guy’s and St Thomas’ Hospital, for checking everything from Alex’s CV to the drug names and uses.

The most important group follows. My sister, Wendy Charell, gave me advice and encouragement, and a very expanded Hermetic reading list. I am in your debt. My step-mother-in-law and true friend, Dorothy Bromiley Losey Phelan: darling Dot, having much in common with Diana Stafford, you were nearly the dedicatee of this book, but Gavrik’s claims had to come first. Thanks to Alison Cathie at Quadrille, Martin Nield, and Jane Morpeth at Headline. Special thanks to Anne Furniss, my Quadrille editor, who got me going so long ago on the Chartres Labyrinth, believed in me, and fought for this book from the start—despite labyrinthine turns and delays. My editor at Headline in London, Flora Rees, deserves special praise for coping so graciously with my moaning about her copious notes. Flora taught me, very simply, to be a much better writer. My outstanding new agents, Andrew Nurnberg and Sarah Nundy at Nurnbergs in London, and the wonderful Robin Straus in New York: I had no concept of how good an agent could be, in every respect, until I had the privilege of joining up with you—my three graces. Thanks for getting me across the finish line.