On a lovely sunny day Bod and his friends catch the train to the seaside. They are all having a lovely time on the beach, so much so that they don't notice the tide coming in - trapping Aunt Flo on a small rock.

Aunt Flo asks Bod round for tea, she is going to bake a chocolate cake. She asks him to invite their friends as well and to ring her before they arrive to remind her to take the cake out of the oven but Bod forgets to ring her.