The Wench is Dead (Inspector Morse, #8)

That night he dreamed in Technicolor. He saw the ochre-skinned, scantily clad siren in her black, arrow Ed stockings, and he could even recall her lavender-hued underclothing. And in Morses muddled computer of a mind, that siren took the name of one Joanna Franks, provocatively walking towards Dukes Cut...
The body of Joanna Franks was found at Duke's Cut on the Oxford canal at about 5.30am on Wednesday, 22nd June 1859.
At around 10.15am on a Saturday morning in 1989 the body of Chief Inspector Morse (though very much alive) was removed to OxfordsJohn Radcliffe Hospital. Treatment for a perforated ulcerous later pronounced successful.
As Morse begins his recovery he comes across an account of the investigation and trial which followed Joanna Franks death...
... and becomes convinced that the two men who were hanged for the murder of Joanna Franks were innocent...