在这部失落独子心家庭片中,本片细腻而不失幽默地讲述了一个五岁孩子从享受专宠到初为人兄的心路历程。小马尔森本是家中享尽父母娇宠的独生子，可是即将出世的妹妹威胁着他的地位。为了迎接小妹的降生，父母日夜忙得团团转，不再有时间关注马尔森；更让他伤心的事，为了避免宠物对妊娠妇女潜在的危害，妈妈竟然决定把马尔森最心爱的宠物肥猫送走。失落之余，昔日的宝贝独子该到以行动反抗的时刻了...
Nina, the mother of five-year old Morrison Glas is about to give birth. She is a vet. The father, Steven, has a small garage, next to their house. Nina and Steven love Morrison very much, but they are too busy to spend time with Morrison, because of their busy lives. When Morrison discovers that the new baby will get his room, he is afraid that he will have to move to tante Zuster, an aunt of his father. Now Morrison is determined, he will not move to tante Zuster! When the baby unexpectedly is about to be born a week early, Morrison has to be taken to tante Zuser in the middle of the night. Morrison thinks up a plan and gets away. He goes into hiding and a giant search is organised by the police and the villagers. When he also 'kidnaps' his newly born sister 'Simone', Nina and Steven have no clue what to do. How will this adventure end for Morrison and his little sister?
