The notorious bachelor and no longer quite so successful ladies’ man Max (Heiner Lauterbach) has furnished his new apartment to his complete satisfaction, but suddenly the enchanting Lisa (Sandra Speichert), the sister of his flatmate and companion Ulli (Michael Roll), turns up on the doorstep and asks if she can stay for the next four weeks. Of course she can, Max thinks to himself, sensing a new conquest. But suddenly Lisa isn’t quite so attractive when Max realises that she has not come alone: she is with her delightful baby Maya (Maya Lauterbach) – and all at once Max sees the situation in a completely different light. How are he and Ulli supposed to win the architectural contest held by the city government when a small child is constantly babbling in his ear? Ulli insists that they have to help Lisa... and when push comes to shove he presents Max with an ultimatum: either the mother and baby can stay, or he will move out. And that will mean they can't enter the architectural contest. So Max grits his teeth, and before long Lisa and Maya have turned the bachelor apartment completely upside down. When Maya makes up her mind that the only way she will fall asleep is in Max's arms, he is forced very much against his will to become a babysitter. And after all, Lisa has to make some money as quickly as possible so she can move out again. It is at this point that Max realises every cloud has a silver lining: his luck with women returns at precisely the moment that he turns up in the playground with the cute Maya. None of the attractive young mothers could possibly suspect that he is merely pretending to be a single father. But before long the lies he is forced to tell in this situation get him into deep trouble. And when he and Lisa begin to find each other attractive, his deception almost proves to be his undoing…