"Allen’s third visit (after Kiss of the Spindle) to her lightly supernatural, steampunk fairy tale world is a clever riff on the “Rapunzel” story that blends exotic undersea travel with a dark mystery and a glee-inducing, respect-first romance between awkward colleagues. The setting seamlessly merges mechanization and magic with Victorian social concerns. Mysterious Romanian count Dravor Petrescu arrives in London claiming to be the unknown uncle of Hazel Hughes, a brilliant physician’s assistant and healer. All her life, Hazel has dreamed of having a twin; Petrescu says he has the twin in his castle, Coppergate, and wants to take Hazel to meet her. Hazel’s employer, friend, and secret admirer, surgeon Dr. Samuel MacInnes, insists on accompanying her on the count’s submarine. Allen’s comedic writing peaks in Sam’s sarcastic automaton butler, Eugene, playing on the tropes of both the overmeticulous British servant and the hypercompetent android. Though the novel stands alone perfectly, series fans will appreciate cameos by the strong heroines of the earlier installments. Readers who love witty adventure-romances between competent, mutually reliant equals will gobble this one up." - Publishers Weekly, starred review

"A fantasy-laden Victorian era tale whose fascinating world is filled with drama and adventure. The adventure aspects of the tale are engaging and tense. An entertaining romance set in interesting lands." —Foreword Reviews