It's still a mystery what happened to Lynette at the end of the prologue, but it seems like whatever happened has changed things at Callum’s house. At the very least, Sephy is no longer welcome there. Callum flinching at the sight of Sephy’s house, though, shows that he’s not welcome
there anymore, either. Hugging Sephy so hard it hurts introduces an element of violence and pain to Sephy and Callum’s relationship. They’re friends, and they have feelings for each other, but those feelings are confusingly intertwined with pain.