The mortality of parents
For Jessica, the very premise of the book is a painful irony. Her mother Donna has died. This is ironic in a dramatic way because the factual knowledge of death is a natural irony: We know about death for a long time, but then one day, death takes someone away whom we feel we need, someone who seemed immortal to us. For Jessica, every day of life is now extremely sublime, because even her experience of her own father is radically new in light of Donna's mortality. Jessica finds dead bodies as a symbol of her new death awareness.
The random dead bodies
The bodies are ironic in both a dramatic and a situational way. They are dramatic because no one knows how they got there or what this means. They are situationally ironic because one does not expect to find dead bodies in one's freezer. The dead bodies are intermingled with the backstory of Donna's life before her untimely death by cancer, so that the reader can easily deduce a symbolic connection between the dead bodies and Jessica's mourning of her mother.
Donna's missing witness
As noted above, Donna's experience of the dead bodies would have been a very helpful part of solving the crime of the double homicide, but that does not happen because death has ended Donna's ability to bear witness. Now she doesn't talk or even remember, on account of her being dead. This is highly ironic, because during the very time when Jessica needs her mother's insight most, she happens to be mourning the end of that insight. The irony points to the absolute nature of death.
The irony of suffering
A symbolic commentary is made on suffering. This is shown through irony, because Jessica happens to be a skillful social worker and can therefore actively reveal what dramatic irony conceals about two dead bodies. She discovers that their whole lives were painful and that they were the victims of severe injustices like abandonment and rape. This provides a whole new ironic spin on death. Jessica turns around from her death fixation to remember the absolute strangeness of human suffering. Is life just tortured survival and untimely death? It is a painful question, clearly.
The ironic ending
The novel ends rather unceremoniously, without any real catharsis for the built-up tension of drama that occurs throughout the murder investigation. The end of the novel might as well be, "And then things kept happening." It does not resolve. This irony is symbolic because it points to the lack of resolution one would expect to feel when examining the issues of suffering and death. That is why those subjects have spawned innumerable religions across the earth, because the questions are not easily solved.
