In Notes on Your Sudden Disappearance by Alison Espach, main characters Sally and Billy form an unbreakable bond after they both witness the death of Sally's older sister Kathy, who is Billy's girlfriend. Research on shared traumatic experiences shows a clear pattern in which people who have endured the same trauma often have a strong magnetic bond, despite the popular notion that shared grief tears love apart.

It's important to first understand the difference between the psychological concept of trauma bonding and the relationship between people who have shared traumatic experiences. Trauma bonding is a bond formed between an abuser and the abused. This is also commonly known as Stockholm Syndrome.

The bond over a shared traumatic experience is completely different, like the relationship between Sally Holt and Billy Barnes in Notes on Your Sudden Disappearance. In Billy and Sally's case, they are bonded in a way they can't be with the other people in their lives, because they ...