Wren is Shark Heart’s protagonist. She is highly organized and practically minded, with an unspecified job in finance. The narrator explains her reasons for being this way, telling readers, “Her routine was even, predictable, and managed. She would do almost anything to protect her ordinariness. […] Some might consider Wren’s life boring, but boring missed the point. She was unshakable” (15). This fear of being unsteady stems from the instability of her childhood, when her mother Angela’s mutation diagnosis made everything in her life uncertain. Part 2 explores this backstory in detail, laying bare the reasons for Angela’s dysfunction and the effects of that dysfunction on Wren.

Because of her troubled past with Angela, Wren has a complex relationship with motherhood. She is hesitant to become a mother, despite pressure from Lewis’s parents and others, because of how motherhood stifled the course of Angela’s life. Nevertheless, she begins longing to have children with Lewis, and this desire becomes an unspoken wish over the course of her time caretaking for him. Her realization that she is pregnant during the Epilogue functions as a deus ex machina moment, resolving the internal conflict she felt over whether to become a mother.