The speaker notices fallen leaves slipping into their boots, and the poem turns this small annoyance into something playful and a little mischievous. The leaves are imagined as if they've just discovered flight and "gone off the handle," eager to dive even further down. Then they become "agents provocateurs," troublemakers stirring things up.
The lines about "going to and fro in the earth / and walking up and down in it" echo a biblical phrase, where it describes Satan, and the poem makes the link explicit by comparing the leaves to "old scratch" with a job to do. That gives the scene a wry, mock-serious tone.
The speaker seems more amused than irritated. The final lines shift to admiration: the leaves' "bold and lurid / colors" are a flashy way to go out, like painting the town red. The mood is light, witty, and quietly celebratory, finding energy and showmanship in decay. The title's "decadence" fits: autumn's dying is treated as a party.