Never the Twain is a gothic crime novel set in Victorian Whitby and Glasgow. When Elizabeth Buchanan an actress, gives birth to identical twin girls, she does not intend to be burdened with them and leaves them in Whitby in the care of her sister and heads back to London. Seventeen years later the twins lives take an unexpected turn when the woman they have always known as their mother dies, leaving them penniless. Elizabeth does not intend to be saddled with the twins again. She places them in a high class brothel in the care of Velda Jansen to have their virginity auctioned to the highest bidder. When Captain Driscoll, a wealthy shipping tycoon visits the brothel they hope he will rescue them. Although the twins are identical he can tell them apart and wants to marry April. Before the twins are deflowered he pays the madam handsomely to free both twins from the brothel. April however, fears they have swapped one form of slavery for another. He proposes to April but is refused. May, finding herself in the lap of luxury in Glasgow is frustrated at her twin's intransigence and begs her to marry him but sets about trying to attract him for herself. He courts April and marries her. May is jealous and manipulative but prepared to wait to get the man she loves. May gets her opportunity when April fails to produce an heir. Her sister offers to take her sister's place in the marital bed hoping to produce a son that April can pass off as her own. Edward, however, is the only person besides their mother, who has ever been able to tell them apart so May's plan has to be devious and carefully constructed. Over the years April has learnt to love Edward, she does not want to share him. He is desperate for an heir and takes to drink in frustration. May convinces April he will tire of her without an heir and devises a plan where she sleeps with Edward. April agrees to the plan. Although she does not want to lose him she sees adopting her sister's plan might secure both their futures. May has always loved Edward and now she is to have him. The sisters know he can tell them apart but reasons if it is candlelight and he is intoxicated, then he can be tricked. The plan works and May becomes pregnant. May and April return to Whitby to hide her pregnancy. They convince Edward that April is the mother through elaborate plans devised by May. May gives birth to a son and reluctantly gives him up to her sister. Edward finds out he has been duped and gives April an ultimatum; her twin has to go. He suspects May is the one who devised the plan. He forgives April and banishes May. Driven by jealousy May poisons him. When the murders are discovered the authorities do not know which twin to prosecute as they cannot tell them apart and both are confessing to the murder. The day before May is to hang they switch roles and May goes home leaving April to hang for the murder she did not commit. On the same day that April hangs, May smothers her son and kills herself. Before killing herself May sends chocolates poisoned with nicotine to her real mother whom she blames for everything that has happened.
