Seppi is in for a real heatwave this time! The first sunny weeks of the year have arrived, and as the temperature outside rises, Seppi's desire for school and annoying teachers plummets. When the new school mascot becomes a victim of a crime, Seppi suddenly finds himself the main suspect in a real criminal case, which puts a lot of pressure on him and his group of friends, the Chillers. After all, Seppi doesn't want to let this suspicion stick to him, so he sets out to uncover the true culprit amidst swimming pool outings, school stress, and pranks on teachers. But is he really as innocent as he wants everyone to believe?.