Starting high school was never going to be easy for Mo, but a fall out with her so-called friends leaves her lonelier than ever. Then she finds Onyx. Exploring an abandoned Victorian asylum may seem a weird way to develop a friendship, but then Mo has always found she does things a bit differently. Together they help each other accept their own differences even when others struggle to do the same. Determined to keep the pair apart, Onyx's dad actions force them back to the secrecy of Denham asylum. On Halloween night, with the old building due for demolition, the two friends enter for the last time.