Highway Robbery by Kate Thompson

The rider sprang off as light as a cat and pulled the reins over the horse's head. Then he marched straight over to me and put them into my hand.

"Hold the mare for me, lad. And when I come back, I'll give you a golden guinea."

A dark stranger leaves his magnificent horse in the care of a boy he's never met. As dusk falls, others offer to pay the boy handsomely for the animal. Then soldiers arrive, demanding to know where the horse's owner has gone.

Could the stranger be the notorious Dick Turpin, known for his daring holdups and amazing exploits? Is the horse the legendary Black Bess? And will the boy ever see the reward he's been promised?

There's mischief in the air, but it isn't entirely clear who's causing it.