Laura Fairlie and Anne Catherick are described as parallel figures. Their striking physical resemblance turns them into each other’s doubles. Walter first meets Anne, but but falls in love with Laura. Even though Walter does not acknowledge this, it is possible that he first develops feelings for Anne, and revives this romantic feeling in Laura.
Anne’s emotional suffering and imprisonment in the asylum foreshadow the suffering and imprisonment Laura will soon endure, thus making Anne the perfect double for Laura. Anne’s imprisonment in the asylum indicates that Laura’s marriage is also a form of imprisonment which can turn a healthy woman into an emotionally deranged person. Laura’s intense suffering at the hands of her husband’s persecution indeed turns her into an emotionally disturbed woman. Laura loses part of her wit and memory after her imprisonment in the asylum. In the story, Laura endures all the sufferings which Anne had been subjected to.
The final revelation that Laura and Anne are actually half-sisters clarifies their physical resemblance to each other, and why they have shared parallel experiences. At the same time, Laura's fate eventually turns out to be happy because she is born legitimate, and therefore entitled to wealth, privilege and education. Anne's fate is much more grim because she grows up in poverty and has no one to help or protect her.