Duncan Campbell leaves Australia to buy the ancient Castle Airde in the Scottish Highlands, which at one time protected the legendary William Wallace. A mysterious collie dog appears, that leaves no footprints in the snow. Youngest child Dottie says she sees a 'Big Man' in the chapel. Lachlan MacGregor, a local carpenter helps the children with money-making schemes, and they befriend Mary Sinclair, the local 'stringer' - a writer for The Edinburgh Rocket newspaper. They meet the quirky locals - the quaint Ghillie and the hiccupping Mrs MacGivacuddle, along with the nasty Major Fordyce and his English Bulldog Magnus, the meddling Mrs Meddle, and their wicked accomplices, Boris, Thumper, and Dingbat. There could be a ghost! There could be a monster! There certainly is a kidnapping - with the hostages thrown into a cold, dark dungeon on Christmas Eve! Will the very nasty Major Fordyce win the day? Or will Scottie the wonder dog help the Campbells live happily ever after?