'A funny, wild, crazily imaginative debut.' The GuardianA National Book Tokens 'best new children's books of 2025' pickThe universe makes no mistakes…Twelve-year-old Arian never wanted a foster sister, much less the weird and annoying one who has joined his family. From her outlandish outfits and bizarre behaviour to her claim that the random stick she carries is a magical weapon, Madlock is creeping Arian out. There’s just one thing the pair can agree on: that she’s from another planet. Of course, Arian never meant literally…When Madlock summons a portal to another world, Arian is launched into an adventure of intergalactic proportions. For an ancient enemy is stirring in the shadows, and the universe has a bigger plan for them than the pair could ever have imagined