A speaker sits in a tavern, drinks far too much, and ends up seeing a unicorn. It is not an ordinary unicorn, though. It belongs to the king's hunt, and it is hanging in a church, as if it were a tapestry or painted image. The word "again" in the last line suggests this has happened before, so the vision feels like a habit as much as a surprise.
The opening is tangled. "Ill with pleasure ill took" plays on the word "ill" and seems to blend sickness, wrongdoing, and enjoyment. The speaker is enjoying themselves and suffering for it at once. That mix gives the poem a woozy, guilty mood, as though the lines themselves are swaying.
The tavern and the church sit side by side, one a place of indulgence and the other of reverence. The unicorn, often a symbol of purity, appears caught and displayed, which adds a faint sadness. The poem seems to suggest that overindulgence can blur the sacred and the earthly into one strange sight.