"The Incontrovertible Truth"
Might be the summer heat has addled me but I really enjoyed "The Incontrovertible Truth" -- probably more than any other episode in series 3.
It seemed to just be simply a reasonably good mystery. I found the lack of character angst a relief (the little girl is returned to her father, Susan Hart is no where to be seen), and the sciencey stuff about finger prints interesting.
I find Edmund Reid and the rest of the Ripper crew is my TV version of comfort food these days.... soon to be disturbed by a goodly dose of "Hannibal" and "Defiance" -- which will sure give me indigestion, if not nightmares.
"If you want a happy ending, that depends, of course, on where you stop your story."
Orson Welles