The truths which are released within the thriller form are compressed, speeded up and distorted... they appear at last, involuntarily, as if emitted from within the repressed corsets and buttoned up modesty of extravagant Victorian costumery.
In The Alibi, Du Maurier has the protagonist sublimating his urge to random murder, which, as it seems to him, has arisen as a result of the conventionalised relations which imprison him. The character thus leads a double life, as an office drone by day, and a primitivist artist by night – but then he is arrested, and confesses to committing, a murder which is not a murder.
The internal logic of the thriller is thus set out: just as the character cannot be held responsible for the crimes he has only thought about, so he is to be found guilty of the crimes that have not been committed.
In Family Plot the deliberate erasure of a motive, thought or act by the subject as it attempts to cover its tracks must always leave a forensic trace of evidence in its place. However, and this is the twist or (to use the fashionable term) the swerve in Hitchcock, the trace that is left at the erased site does not draw the investigator back to that event but leads him on to discover something else, something even more incriminating, but which is not at all suspected by the subject himself.
The primal scene is thus deduced precisely because it is inaccessible. As the investigator reaches a dead end in pursuit of evidence for the original crime, the trace of its erasure leads him to discover other acts which the subject does not yet know he is guilty of. The investigator, at the dénouement, functions as an instrument for realising the subject’s fatal knowledge of himself.
Both Du Maurier and Hitchcock suggest that conventional people have the same baroque motivations as society’s extremists. Conformists are as perverse as revolutionaries – they are moved by the same forces. Extremity exists in all corners and persists as long as it remains hidden; extreme and unrecognised passions are the essence of the internal life.
A comparable thought occurs to Sherlock Holmes:
"Good heavens!" I cried. "Who would associate crime with these dear old homesteads?"
"They always fill me with a certain horror. It is my belief, Watson, founded upon my experience, that the lowest and vilest alleys in London do not present a more dreadful record of sin than does the smiling and beautiful countryside."
"You horrify me!"
"But the reason is very obvious. The pressure of public opinion can do in the town what the law cannot accomplish. There is no lane so vile that the scream of a tortured child, or the thud of a drunkard's blow, does not beget sympathy and indignation among the neighbours, and then the whole machinery of justice is ever so close that a word of complaint can set it going, and there is but a step between the crime and the dock. But look at these lonely houses, each in its own fields, filled for the most part with poor ignorant folk who know little of the law. Think of the deeds of hellish cruelty, the hidden wickedness which may go on, year in, year out, in such places, and none the wiser."
The Copper Beeches