In 1244, a group of Icelandic men riding across a windswept ridge saw something come out of the weather and cross the road in front of them. The account that survives gives us three words in Old Norse. Tröll eitt mikit. A great troll. Then the story moves on, back to the feuds and the politics, as if a monster in the road was barely worth the ink.

Carol Ann, host of the paranormal documentary channel The InBetween, spends this evening chasing that one word.

She'll take you back through the medieval sagas, where a troll could be a giant, a witch, a ghost, or a neighbor who had stopped being quite human. Into the Swedish folk archives, where trolls kept cattle, wore fine clothes, raised children, and occasionally asked a farmer to please move his barn, because the runoff was leaking onto their dinner table. Past the 1800s illustrators who gave the troll the face we all picture now, and who we've mistaken ever since for the tradition itself. And forward to a road crew in Iceland who buried a stone in 2015, watched the road flood and the machinery break down, and went back out with an excavator in 2016 to dig it up and wash it clean.

Along the way, three people from the last hundred years who say they met one, in their own words.

It's a story about how a word changes, what we do to the creatures we inherit, and why a modern European government moved a fifty-tonne rock rather than break it. Come for the trolls. Stay because the ones in the old records are stranger, and better, than the ones on the souvenir shelf.