The Time Travels of Arabella and Tom: The Vikings

Arabella Twigg is a very ordinary girl living with her peculiar family. Her life is quite boring – until strange things begin happening to her.
At school, Arabella is learning about the Vikings and is most interested. So much so, that when on holiday with her family, her horrid brother Tom, takes her out on a rowing boat and they find themselves captured by Vikings.
They are taken back to the Viking village and are forced to go with them when they ransack the monastery at Lindisfarne.
How can they help the monks? How can they get back home?