Sabrina falls out of the modern world and into the ancient one, where she turns her wits into a merchant fortune and uses it to make Harrison a duke. When he brings home a scheming concubine and lets her dismantle the household, Sabrina stops investing in a man who already spent her.
She hands her fortune and her modern ideas to her granddaughter Harriet, then returns to her own time. Now eighteen again with a family that loves her, she watches Harriet use those lessons to take the duke's mansion apart piece by piece, while Harrison learns too late whose money built his title.
