Well, we knew he did it but how was Jane, played by the very watchable Claire Goose, going to prove it?
Although last night's concluding part of ITV thriller Undeniable was following a predictable path - young mother who, as a child, witnessed her own mother's murder spots the killer but no-one believes her due to her fragile mental health - there was a twist.
A DNA test has seemingly let the accused man, respected doctor Andrew Rawlins (Peter Firth) off the hook. Jane, whose obsession with nailing her mother's killer, takes precedence, according to her husband, over her own family continues her dogged pursuit of her man while her life slowly unravels.
Even the detective, played by Pippa Haywood, now facing 'retirement' from an apparently ageist police force, who handled the original case, urges her to move on before a tenuous lead as she's clearing her desk, puts her back on the scent again.
Jane's discovery of a first wife who had - somewhat conveniently for our story - suffered years of abuse from our suspect and who, when confronted by her lawyer daughter, confessed to suspecting him of the murder all along, seemed a little contrived.
What the first wife did reveal however was that since the murder Andrew had been diagnosed with leukaemia and undergone a bone marrow transplant which meant his blood had been changed - he was now a chimera. Who knew?
A vindicated Jane finally gets her man and is reunited with her family - a pleasing finale to this engaging and extremely watchable two parter.