Cuba found the booklet in a bin of returns, between a mushroom atlas and a comic book. The cover whispered in fluorescent font: Invisible Cat Owner's Manual, Second Edition. It sounded like a joke, so of course he took it for a break. Zosia looked at the table of contents and immediately burst into laughter. - 'Point one: don't treat the cat like air or it will get offended,' she read. After the lesson, Kuba checked whether it was marketing or a real disaster in the box. He put down a bowl of milk, scattered some flour and waited for a miracle. The milk disappeared, the flour trembled and four delicate imprints appeared on the countertop. Something invisible rubbed his calf, then nudged the cardboard box with his knee. Cuba squealed, but pretended it was an attempt to alarm the fridge, for dignity's sake. In the instructions, someone had added with a pen: Likes radiators, ignores physics, hates pickles. The next day the school declared a Pet Day, with a parade in the gymnasium. - Will you bring a cat? - asked Zosia, already preparing a banner: the Imagination Supporters Club. - He's not imaginary, he's lowly visible,' corrected Kuba, very serious. The cat, invisible as an Internet password, rolled a sandwich out of his backpack. The rustling, self-carrying paper attracted the gaze of Director Ploska. - 'Please don't bring in food ghosts,' she said, and the corridor erupted in giggles. In the evening, Cuba continued reading the rules as the card with the number eight was crumpled. Don't feed the cat silence after twenty-two or it will start eating sounds. Don't repeat the word blank three times with the window open in the schoolroom. If you forget, the cat will stop being discreet and bring someone uninvited. Cuba pulled back the curtain to ventilate, and whispered blankly once for a joke. Then a second time, because no one was looking and the cat was purring like a hairdryer. On parade, the hall window stood open and the microphone hissed like an angry kettle. The cat sat on the pennant with an invisible weight until the pole crackled quietly. - It's quiet in here somehow, so empty.... - sighed Zosia, correcting the letter Y on the poster. - Don't say that - hissed Kuba, but someone at the back added reflexively: empty. A third blank stuck on Kuba's tongue as the instructions suddenly flashed in his pocket. The window squeaked open, the air swelled with the trace of a paw, and Mrs Pliskova grabbed the handle.