Colin Dexter based this Morse novel on a real case, that of the murder of Christina Collins in 1839 whilst travelling by canal from Staffordshire to London.
The title is from Christopher Marlowe's play, "The Jew of Malta," probably written in 1590. "Thou hast committed/ Fornication: but that was in another country,/ And besides, the wench is dead."
Although this episode does not feature Lewis, he is present in the 1992 radio version, portrayed by Robert Glenister.