When You Left is a picture book for 4-8 year-olds, and explores the theme that when parents break up and one parent moves on, it's okay to have muddled feelings. A child's parents split up and a new parent, Alex, has come on the scene. While the child desperately wants their parents to get back together and wants to dislike the new parent, there is a realisation that the sadness gets better, there can be room to love another parent and that the future can look hopeful.