Get out the microscope, because we’re going through this poem line-by-line.
They had tied her up to attention, with many a sniggering jest.
They had bound a musket beside her, with the barrel beneath her breast.
- Not only do the soldiers tie Bess up "at attention" (as if she was a soldier standing up at attention), they make fun of her too. They make "sniggering jests" (mean little jokes).
- Then they tied up a gun next to her, with the barrel pointing right at her chest. Maybe they did this to scare her, to keep her in line, although the speaker doesn't exactly say.
"Now keep good watch!" and they kissed her. She heard the doomed man say--
Look for me by moonlight;
Watch for me by moonlight;
I'll come to thee by moonlight, though hell should bar the way!
- Then they tell her to "keep good watch," which is a pretty cruel joke, since she'll be watching her boyfriend get murdered. Then they kiss her, just to be sleazy as well as mean.
- If these guys were in a cartoon, they'd be twirling their mustaches and laughing maniacally.
- Bess can think only of her "doomed" highwayman, and she remembers his promise to come back by moonlight. The speaker repeats lines 28-30 just to remind us what the highwayman said.