Miles's sporadic recollection of memory fragments that bring him back to the night his mother died generates much of the suspense in Past the Shallows. By the end of the novel, Miles pieces together the complete picture of what occurred during the traumatic night he sat in the backseat of her car and witnessed her death.
Miles's inability to remember the full truth of what happened on the night of his mother's death can be seen as an expression of dissociative amnesia, a psychological condition in which a person forgets key information related to their life and identity.
Dissociative amnesia affects people differently. For some individuals, the amnesia limits their ability to recall important details about a specific event, or even a series of events that share thematic relevance. For instance, victims of abuse may instinctively block out all memories of having been harmed. This instinctive selective forgetting is largely understood as a psychological survival mechanism whose purpose is to guard a person against traumatic memories so they do not have to experience again the pain and stress of the traumatic event or events. In rare cases of dissociative amnesia, a person may forget everything about their identity and may even adopt a new identity.
Clinicians and therapists use a variety of therapies to treat patients with dissociative amnesia. Through psychotherapy, cognitive-behavioral therapy, hypnosis, or other treatments, practitioners aim to help the patient safely manage their painful memories and develop new means of coping with their trauma.
