The question is, do you read the Wikipedia entry for John Christie before watching Rillington Place, or after?
The 2016 BBC mini-series currently screening on UKTV tells the story of one of Britain's most notorious 20th-century serial murderers: Christie strangled at least eight women in London between 1943 and 1953.
A brief overview of his gruesome criminal record certainly does no harm in advance of viewing the purposefully murky opening episode.
Each of the series' three parts plays out from the perspective of a different character. The first is focused on Christie's wife, Ethel, shading in the corners of the pair's strained, joyless marriage and building a portrait of the man behind the murders. Through her eyes we get an unrelenting feeling of unease, but just what her husband is up to is never made explicitly clear.
Series director Craig Vivieros has form for this kind of thing. He also directed the BBC's 2015 adaptation of Agatha Christie's classic And Then There None, injecting a similar sense of dread into every corner of that period murder story's house on the hill. The setting here is more humble: we join the action as Reg and Ethel move into the perpetually dark and dreary downstairs flat at number 10 Rillington Place, in a bleak pre-Hugh Grant and Julia Roberts Notting Hill. "Apparently it's a very sought after area," he unconvincingly sells it to her as the pair pick a path to the front door through piles of horse manure.
Much of the action in the first part plays out inside the flat, which remains largely unchanged despite the time period spanning a decade from 1938 to 1948. The impression you get is that Ethel barely left 10 Rillington Place other than to go to her job as a typist.
Her husband, meanwhile, spends most of his time away from home – Christie worked as a policeman during much of the wartime, despite the long list of prior convictions which saw him in and out of prison over the preceding decade.
Samantha Morton is superbly restrained as Ethel, keeping a stiff upper lip, staring into the distance, and blaming herself, blaming the misery of wartime London, blaming everything but her husband for his increasingly "strange mood". When she does go to the doctor with her concerns about him she gets told he simply needs more "care and attention" from his wife.
Portrayed with quiet menace by Tim Roth, the killer is a mumbling, shuffling, quintessentially dour mid-century English character. With his bald head, specs and suspenders he looks like a man in a Lowry painting or a Raymond Briggs drawing come to life.
Over time the full picture begins to reveal itself to us as it does to Ethel. She follows her husband one night to nearby boozer The Winchester and sees his unmistakable set of suspenders following two women into a side room. "One of 'em were playin' wi' yer 'at," she accuses him. Later she overhears his advances on a new colleague's partner, telling her he trained as a doctor before the war. "You were a St Johns ambulance volunteer," she corrects him. He later returns the favour by pinning her against the wall and strangling her within an inch of her life.
All very grim and ominous, but the first part of Rillington Place is a slow burn that's never anything short of completely captivating. It's a bold move for a show about a serial killer to go the whole first episode without a murder, but here it's all the more rich and suspenseful for it.
In part two the focus shifts to Timothy Evans, whose wrongful execution for the murder of his wife and daughter we saw as a flash-forward at the start of part one . At the end of the first episode Evans and his wife Beryl move into the upstairs flat at 10 Rillington Place, Christie spying on them through a hole in the kitchen wall. "Is she pretty?" Ethel asks. The edge of the jigsaw has been built, now for the pieces to fall into place.