Tiny Tim is back! No, not the squeaky-voiced troubadour who tip-toed through tulips in the 1960s, but the original--Timothy Cratchit, the crutch-wielding tyke from Charles Dickens's A Christmas Carol. Only now he's a "mostly able-bodied" 23 years old, resides in a London whorehouse in exchange for tutoring the madam, struggles to wean himself from financial dependence on his ancient "Uncle" Ebenezer Scrooge, and, as we learn in Louis Bayard's darkly enchanting historical thriller, Mr. Timothy, is haunted by the spirit of his late father--a man whose optimism and strength the son feels himself incapable of imitating. When we first encounter Timothy, during the Christmas season of 1860, he's vexed by the discovery of two dead 10-year-old girls, each branded with the letter "G"--one found in an alley, the other fished from the Thames River by Cratchit and a voluble old salt who makes his money by finding (and then robbing, of course) errant corpses. Timothy's concern leads him to protect a third possessively marked waif, the frightened and suspicious Philomela--who, he soon realizes, is being sought by a knife-loving former Scotland Yard inspector and a moneyed, malevolent voluptuary. When, despite precautions, Philomela is kidnapped by her pursuers, Cratchit--assisted by a shrewd warbling urchin known as Colin the Melodious--resolves to fulfill his "great calling" in life by mounting a rescue. However, this mission will force the habitually uncourageous Timothy