Usha is devastated when her grandmother Kali Ma passes away. Not quite fitting in at school, with her best friend moving away, and with an annoying new adoptive sister arriving, Usha feels lost. That is until Kali Ma's ghost appears...with a task for her. Usha's family home is full of history and secrets. Many years ago it was The House of the Ayahs - for those nannies who couldn't return to their Indian homeland - and Kali Ma made a promise she couldn't keep. She can't pass on to the other side until Usha fulfils it. Today, Usha's over-worked parents run the house as a home for refugees, but eviction threatens. The precious historical lease documents that could save them are lost. As the house slowly fills up with ghosts, that only she and her new sister Emtiaz can see, Usha realises she has more to save than just her grandmother's ghost. Usha and Emtiaz must work together on a quest through London, accompanied by two bickering ghosts, to find a series of objects that shine a magical light on their family's past and hold the clues to securing their future. If they can set the secrets of generations free, will they be in time to save their home?