It all started on Monday morning, when Bartek, Lena and Maks ran into the school cloakroom in an attempt to get away from Mr Janusz from Maths, who had just announced an unannounced mid-term. Their plan to avoid the class was simple: pretend to look for the lost sock monster that had been rumoured for a week. ‘I swear, I saw him on Friday!’ said Maks, with a seriousness worthy of Sherlock Holmes. ‘He was wearing a cap with a pom-pom and chewing on a school bell.’ Lena rolled her eyes. ‘Maks, you’re a sock monster. You’ve brought the wrong pair again!’ But then something strange happened. A quiet… giggling? Bartek froze, Lena jumped up, and Maks pulled a torch out of his pocket as if he always carried it with him (and, importantly, he actually did, since once he couldn’t find a bun in his backpack). ‘Okay, we’re looking for evidence,’ whispered Bartek, and Lena added with a hint of amusement: ‘If we find the monster, I’ll make him do my homework for me.’ As they got closer to the locker, they heard a quiet ‘Attention: the maths patrol is coming!’ ‘Is your locker talking?’ Maks asked in shock. ‘Mine doesn’t, but I think this one does,’ replied Lena. Meanwhile, a shadow began to approach the cloakroom. It was definitely NOT Mr Janusz. It was someone they had never seen in school before. The shadow was wearing a giant hoodie with pink socks with yellow bananas sticking out from underneath. The giggling subsided. The friends froze. All that could be heard in the cloakroom was the beating of their hearts… and a very suspicious smacking. Who was the mysterious visitor? What was he doing in their school? And, above all, why was their locker talking?