The romantic tales are clear in outline; this is not.

But the elements in the original story entered, as it were of their own accord, into Browning.

There are several curious, unconscious reversions to folk-lore which have crept into his work like living things which, seeing Browning engaged on a story of theirs, entered into it as into a house of their own, and without his knowledge.

The wretched cripple who points the way; the blind and wicked horse; the accursed stream; the giant mountain range, all the peaks alive, as if in a nature myth; the crowd of Roland's predecessors turned to stone by their failure; the sudden revealing of the tower where no tower had been, might all be matched out of folk-stories.

I think I have heard that Browning wrote the poem at a breath one morning; and it reads as if, from verse to verse, he did not know what was coming to his pen.