I identify two sets of problems in the story, the adolescents trying to find an identity for themselves and the Mr. Pignati 's loneliness. Both of these issues lead to the bigger problem that becomes the catalyst that changes everything.
Mr. Pignati has a stroke when he is roller skating through his home with the kids. He has to go to the hospital. The two kids, John and Lorraine, decide to have a small party without permission. The party gets out of hand and the teens begin to destroy the items in the home that Mr. Pignati values. They smash his pigs and bust different things up. One of the kids tries to steal from Mr. Pignati and so John gets into an altercation with him.
The police arrive and breaks things up at the same time as Mr. Pignati arrives home from the hospital. After he forgives the children they all go to the zoo and visit Bo Bo and learn that he and another baboon died. Mr. Pignati lets out a cry and dies. He had been alone except for the freiendship of the baboons.