"Where gat ye your dinner, my handsome young man?"
"I dined wi' my true love; mother, make my bed soon,
For I'm weary wi' hunting, and fain wald lie down." (6-8)
Here's a pretty good sign that things didn't go well between Lord Randall and his supposed "true love": he gets home feeling down in the dumps, exhausted, and generally miserable. It seems clear to us from this point onward that this is not a happy pair of lovers.
"What gat ye to your dinner, my handsome young man?"
"I gat eels boiled in broo: […]" (10-11)
The specificity here makes us a little suspicious. Why, in this little love song, do we need to hear what Lord Randall's girlfriend fed him? It seems a bit fishy to us (hyuk hyuk…).
"What became of your bloodhounds, my handsome young man?"
"O they swelled and they died […]" (14-15)
Okay. If this isn't a Major Red Flag, we don't know what is. The lurking air of menace that's swirled around this poem from the beginning comes right out and swallows everything up here. We knew we couldn't trust that sketchy girlfriend.
O I fear ye are poisoned, my handsome young man!"
"O yes, I am poisoned: mother, make my bed soon,
For I'm sick at the heart, and I fain wald lie down." (18-20)
Well, that's that. Lord Randall's betrayal by his treacherous ladylove is proven here. though the clues have come in bits and pieces. He seems more affected by heartbreak than by poison, which might explain his reluctance to admit the truth until the end of the poem.