Aaron's father, Mr. Kurlander (Jeroen Krabbé) takes a job as a salesman and leaves Aaron to fend for himself while his mother is in hospital. Aaron manages to survive until his father comes back at the end of the summer and the mother gets over her illness.
Then, they plan to move out of the hotel. If they leave without paying their debts, the hotel will confiscate their belongings, so they simply wear many layers of clothes, throw everything else outside the window, and walk out the door.
Thanks Mary C!