Hetty and the gang play a prank on Sheila, but it has disastrous consequences when a young visitor with a secret arrives to stay at Calendar Hall.

Jack has a romantic proposal in mind, but a new butler spells trouble for the gang, while Ashok reveals his secret - a priceless diamond hidden in Calendar Hall.

The gang follow clues as they search for the Dawn Star, not realising that Ambrose is looking for it, too. Rosamund surprises everyone when she brings an old enemy back to the house.