12 year old Harmony Parker is obsessed with animals. She and her best friend Tom have set up an amateur vetinary practice in a small tent in her back garden yet her parents won't allow her to have a pet. However, hopes of a pet are in sight when Harmony's eccentric and mysterious Uncle Ginger pays her family a brief visit and leaves her with a deceptively normal looking 50 pence piece. Harmony soon discovers that the coin posseses wish granting powers and learns through the course of the series to be careful what she wishes for.

Harmony's first wish from her magic 50p coin is for a rabbit. However, she soon find that her family don't share her enthusiasm for Anita the rabbit. Harmony wishes for her family to change but soon learns that different is necessarily better.

Chaos is caused after Mrs. Parker spend Harmony's magic 50 pence piece. Harmony successfuly recovers it and wishes for a bike. However, with the bike come other things and the results leave Harmony in the doghouse with the rest of the Parker household.

Harmony's precious coin goes missing and a 'kidhunt' ensues. When Harmony discovers that her sister Melody is the cause she vengefully wishes Melody into a rather hairy situation!

The prospect of returning to school after a blissfully unrestrained summer does not sit well with Harmony Parker. She eagerly uses the power of the Queen's Nose to get time off school but somehow ends up in the children's ward of the local hospital. Whilst in hospital, not only do the hospital staff discover that trouble and chaos love Harmony but she makes amends with her sister Melody and grants her wish.