Marcette's poem pictures a grand white palace set in a garden that looks lovely but feels cruel. Almost every image carries violence: red flowers thrash, ivy lurks on an oak where something was hanged, thorns on white roses drip blood, and shrikes, birds known for killing their prey, slaughter. Nothing here is peaceful, even though the setting should be.
The light is the key idea. It "reveals all of the sins" and shows both "ugliness and beauty," so it works less like a gentle glow and more like an interrogation lamp. Nothing can hide. The closing phrase, "blinding agony," makes the light itself painful, as if being seen completely hurts.
The speaker seems unsettled, even haunted. Judging by the word "our," they include themselves in the exposure rather than pointing fingers at others. The mood is gothic and tense: elegant on the surface, ugly underneath, with a sense that something terrible has happened here and the brightness will not let anyone forget it.