I think the poet wants to covey us about guilt. The reason why I think that way is in the 3rd paragraph “Forgive me they were delicious so sweet and so cold”. And also, the writer tells us about why did he ate that plums. Or perhaps I can analyze it to another thing that the writer wants to tell us about a man/women who already know that the plums belong to someone else but he or she going to eat it anyway.