This is a horror story, and a ghost story, and an enormously compelling reflection on what it means to be complicit, to repent, to suffer punishment. Helen Franklin is living a quiet, ascetic life in Prague when her friend, Karel, summons her and shares that he’s being pursued by a strange creature, the mythical Melmoth the Witness. Helen is shocked by her ordinarily stolid friend’s ragged fear and agrees to humor him, but as she learns more about this Melmoth, she becomes pursued herself. This book has much of the same limpid prose that drew me into Perry’s previous book, The Essex Serpent, but it comes with a great deal more contemplation about the nature of evil, as well as the purpose and form of stories like this one.