Ella is staying near the beach in Broome, Australia. The tides there can rise up to nine metres, and they come in really fast. If you're in the water, you might have to run to get out before it gets too deep.
The tides aren't the only things in Broome that Ella finds unusual - there's also the strange couple next door, and the story of a missing schoolgirl. When Ella finds a beautiful bracelet, she believes she knows what's been happening. She goes looking for answers, but what she finds is terrifying.