Part one of a musical special. It's Christmas Eve and Hetty and Gideon are on a charity mission to London when they are caught up in a street gang that is run by Hetty's oldest, most frightening enemy.

It's Christmas Eve and Hetty and Gideon are on a charity mission to London when they are caught up in a street gang that is run by Hetty's oldest, most frightening enemy.

It's Christmas Eve and Hetty and Gideon are on a charity mission to London when they are caught up in a street gang that is run by Hetty's oldest, most frightening enemy.

Hetty and the gang race back to Calendar Hall to stop Ambrose before anyone gets hurt, and to discover the truth about what really happened at the house.

Hetty, on the run in London, is shocked to discover an old friend in the workhouse. Back at Calendar Hall, the gang have a plan to prove Hetty is innocent and that Ambrose is the real thief.

The gang are stunned when Hetty is accused of stealing the Dawn Star, and a fire in the barn leads to a dramatic escape.

The gang are in danger when Rosamund leaves Lady Grenford and Ambrose in charge. Hetty finally cracks the code - but can the gang get to the Dawn Star in time?

The gang realise they need to break through a wall to get to the jewel - but can they do it without being discovered? And what will Agnes do when she finds out Gideon's been lying to her?

Lizzie discovers a secret tunnel with a clue, while the gang races Ambrose to find the jewel, and Hetty fears that Ashok is growing too friendly with Lady Grenford.

Hetty and the gang find crucial clues to the Dawn Star, although Flo and Ambrose are now watching them closely and Lady Grenford appears to know more about the diamond than she's letting on.

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.

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.

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.