How does Wyndham make the Aunt Harriet episode such a memorable and significant part of The Chrysalids?
The significance of this moving and chilling episode in Chapter 7 lies in the way that it foregrounds the importance of the code of deviation in this dystopian world above anything else, including family bonds, and also in its function of foreshadowing the rejection of David and of Petra by their parents and the society at large. Aunt Harriet comes to her sister at the end of her tether. Having birthed a "deviant" for a third time, she recognises that she may be divorced and cast out, and her child killed. Note what she says to her sister and brother-in-law:
I came here hoping against hope for sympathy and help. Emily is the only person who can help me. I--I can see how foolish I was to hope at all...
Harriet had hoped that she could use Petra to gain the certificate declaring her baby to be healthy. The shock and horror of David's mother and father in response to this proposal clearly indicates the way that in this world the rule of deviation is stronger than blood and family ties. The way that Petra and Aunt Harriet's child are born together and supposedly Petra is the only "normal" baby also foreshadows the way that David and Petra's parents will so eagerly hunt them down for capture and torture. In this world there is no hope of sympathy if there is a mutation, and the way that Aunt Harriet is left with no option but to kill herself is a chilling reminder of the absence of hope in this strange dystopian world.