Cassiel is the angel of the twenty-third. Twelve days a year, one day a month, he is aimed by a hand he has never seen at some kitchen, some tent, some ruined harbor, always after the worst has already happened. He cannot warm a cup. He cannot move a cloak. He can only sit down beside the one person who is still there, and stay until midnight takes him. A novel in twelve months: Sacramento the morning after a fire; Messina twenty-six days after the earthquake; a king's tent at Clontarf; a foreign ministry in Belgrade the night an ultimatum arrives; a kitchen where an old man marks a date he has kept for eighty years; and, once, the dark before the first light. Along the way Cassiel learns what the twenty-third is for, and who he was before he was given it. This is a novel with three doors in it. Where the book offers a choice, you make it, and turn to the month it names. You are the hand that aims him. The months you pass over happened; you were elsewhere. A back page keeps the names of the people you sent him to. One path reads in an hour. The second costs fifteen minutes more, if you want to see what the doors do.