Angus and Elspeth MacTout are the son and daughter of the Lochkeeper of the world famous Loch Ness. Their father thinks stories of a Loch Ness Monster are all 'stuff and nonsense'. However, his children know differently. One day they found a creature stuck in a hole and soon discovered that there is not one, but an entire colony of Loch Ness Monsters. As a reward for helping to come up with a plan to free the trapped Nessie (Silly-Ness) the Queen of the Family-Ness (Her High-Ness) gives each of the children a secret thistle whistle. When blown the whistle will summon any Nessie in the vicinity who will come to Angus and Elspeth's aid. Over the course of the series we meet a whole host of different members of the Family-Ness, all of whom are named after personality traits.