| Quote #1 O what can ail thee, knight at arms, |
The knight seems almost ghost-like in these first lines. The speaker finds him all "alone" and "loitering" near a lake. He's pale like a ghost, and the "loitering" seems like a ghost that haunts the place where he died.
| Quote #2 I see a lily on thy brow |
The speaker can tell that the knight has a fever. High fevers can cause hallucinations or visions. Is it possible that the knight is just a sick man who had a feverish dream about a fairy lady who seduced him and then ditched him?
| Quote #3 And nothing else saw all day long (line 22) |
The knight is so obsessed with the beautiful lady that he doesn't even see anything else. He's blind to the rest of the world.