Someone has photographed Karlsson and, to his great horror, Little Brother reads in the newspaper that a huge reward is promised to whoever can catch the "flying barrel".
Little brother and his father buy a Christmas tree that they take home. Karlsson wants to know why they have a tree in the apartment. After Little Brother explains, Karlsson also wants one.
Little brother can hardly save himself before his 8th birthday. Then Karlsson decides that he is also celebrating his birthday. The next morning Little Brother is woken up by the family with cookies, candles, songs and presents.