"If you play with fire, eventually you´re going to get burned" is a popular saying, and we can apply it to Bertha, Rochester and Jane´s lives in this way:
Rochester was pushed to get married to Bertha by her family. He did not know anything about her mental illness, Bertha´s family only wanted to have her off because they knew she could have inherited the illness. But Bertha Mason was very wealthy and beautiful. Rochester becomes an unhappy husband and he lies to Jane about his secret past.
The plot is based upon lies, disappointment, bitterness and this comes to unhappy end: the castle is set on fire by the "secret component". The characters didn´t follow the order of love and compassion.
Brontë gives redemption to them; a second opportunity for Jane and Rochester to start living together in harmony. And Bertha sets herself free through the escape and eventual death in the flames.