Get out the microscope, because we’re going through this poem line-by-line.
Lines 19-21
And dark in the dark old inn-yard a stable-wicket creaked
Where Tim the ostler listened; his face was white and peaked;
His eyes were hollows of madness, his hair like moldy hay,
- Now, all of a sudden, we turn away from the couple we just met, and meet a third character. First we hear the creaking sound of a "stable-wicket" (that means a door or gate in a stable). Apparently someone is eavesdropping on the two lovers.
- It turns out to be Tim, the ostler (the guy who takes care of the horses at an inn). Tim's a crazy-looking guy, with a pinched white face, insane eyes, and hair that looks like moldy hay.
Lines 21-23
But he loved the landlord's daughter,
The landlord's red-lipped daughter,
Dumb as a dog he listened, and he heard the robber say--
- Crazy Tim is also in love with Bess, although it's hard to imagine he has much of a chance. The speaker mentions her "red lips" which helps to emphasize her sexiness and the contrast with poor Tim's white face.
- As Tim listens to the highwayman, the speaker tells us he is "dumb as a dog." In this case "dumb" just means silent, but the comparison to a dog is no accident. We're definitely supposed to notice the difference between the beautiful lovers and this pathetic, ugly servant.