The gothic novel as a genre is commonly associated with "crossing boundaries," particularly, as Gilbert and Gubar point out in The Madwoman in the Attic, when the novel is written by a woman. If the author crosses boundaries of taste and decency by writing about a subject, it follows that the protagonist is even more transgressive for actually performing the acts it is taboo even to describe. The actual boundary Victor crosses in Frankenstein, however, is rendered somewhat nebulous by the fact that what he does is commonly believed to be impossible, meaning that it is not illegal. Societies only bother to make laws against transgressions which the legislators believe might actually occur.
Victor effectively crosses a boundary when his creature does, as it passes from inanimate object to living being. In making this happen, Victor commits moral blasphemy, if not a breach of the law, by playing God. For many nineteenth-century readers, as well as a fair number of modern ones, this would be transgressive even if the creature were happy and a force for good in the world. The fact that it is miserable, and ultimately destructive, makes the moral issue more straightforward, since the effects of the transgression are all bad, particularly for Victor himself. One effect of his crossing this boundary in creating life is his own death.
Victor's secrecy and isolation are at first necessitated by the fact that he is breaking new ground scientifically. This secrecy is necessary for any scientist who wants to stop rivals from stealing his research. However, even before he is successful, Victor's secrecy becomes a burden to him. He asks:
Who shall conceive the horrors of my secret toil as I dabbled among the unhallowed damps of the grave or tortured the living animal to animate the lifeless clay?
This is not the ordinary secrecy of the man who fears that his research may be stolen. The clandestine nature of his work, like its physical cruelty, is intimately related to the morally transgressive nature of Victor's project.