The river's tent is broken: the last fingers of leaf Clutch and sink into the wet bank. The wind Crosses the brown land, unheard
. The nymphs are departed. Sweet Thames, run softly, till I end my song. The river bears no empty bottles, sandwich papers, Silk handkerchiefs, cardboard boxes, cigarette ends Or other testimony of summer nights. The nymphs are departed. And their friends, the loitering heirs of city directors; Departed, have left no addresses.
It sounds like to me that its talking about the theme or the main idea so it will be about how you will have to stay close to your friends and trust each other.
To me the theme is to always stay strong, and trust your friends, stay close, and friendship is important because the story is talking about friendship and how it affected a place...
In terms of the first question, "They" would be an objective pronoun, but it should be noted that this does not have to be so. for the second, the answer is "my".
