Based on real-life events, it tells the story of mild-mannered nurse, Malcolm Webster, who, over a 13 year period set about poisoning and murdering his first wife, trying to do the same to his second, and setting up another deceitful scheme with his third fiancée.
Sheridan plays his doomed first wife, Claire, who is putting Malcolm under pressure over their mounting debts.
Using drugs from the hospital where he works, he begins drugging her to keep her quiet, but when she books a doctors appointment to see why she's been feeling so ill, he takes matters into his own hands and stages a car accident in which she is killed.
Having got away with that one, and cashed in on a £200,000 life insurance police, he heads to New Zealand where he's soon walking down the aisle with his new bride, Felicity.
But he isn't prepared for Felicity's tenaciousness when he starts drugging her too…
The Widower, ITV, 9pm
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