Katy has to stay with her grandfather and cousin Vanessa at the old Mill House while her mother is in hospital. But when she gets there, everything is different. Granddad who use to be a domineering, bossy man seems to be a nervous shadow of himself.
And Vanessa who used to be so friendly has become cold and nasty - and very Gothic. She makes it clear to Katy that she isn't wanted. She's preparing for her surprise party and when Katy asks how anyone can arrange their own surprise party, she says, "Wait and see what the surprise is!"
To make matters worse, there's noises in the attic. Everyone says its just bats, but then everyone seems to be lying.