The Wolves of Willoughby Chase — Joan Aiken

In this chilling beginning to The Wolves Chronicles, two little cousins are left in the care of an evil governess. They escape and travel 400 miles to London with their friend Simon and his geese. A sad and sinister howling arose. It was the far-off cry of wolves "Make haste, make haste! There is not a moment to be lost!" But Bonnie and her orphan cousin discover, the real danger lies not with the savage roaming beasts, but with the sinister new occupant of Willoughby Chase.