An Oxford don's death in an opium den is investigated by the literary detective duo--with some help from fellow author Charles Dodgson . . .   One dank November night, Charles Dickens and Wilkie Collins are called to a part of London notorious for its opium dens--where an Oxford history don has been found murdered. Eager to escape the drudgery of a London winter, the two amateur detectives willingly accept Inspector Field's orders to travel on the new railway line to Oxford, where Collins was once a student, to conduct an undercover investigation.   Once in Oxford, they enlist the help of Collins's old schoolmate, Charles Dodgson (who will soon be known to the world as Lewis Carroll), a brilliant mind on the verge of becoming the youngest don in Oxford's history. Together, they encounter a complex conspiracy punctuated by murder, political radicalism, and revenge . . .   "Vibrant Victorian social history and intriguing biographical details about Dickens" enliven this unique historical mystery with a literary twist from the author of The Detective and Mr. Dickens (Booklist).