When Stella and her younger brother, Tom, move to their new London home, they become mystified by the disappearances of Harry, their elderly neighbour’s small dog. Where does he go? And why does he keep reappearing wet-through?

Their quest to solve the riddle over the summer holidays leads to a boat buried under a grassy mound, and a tunnel that takes them to a secret lake.

Who is the boy rowing towards them who looks so terrified? And whose are those children’s voices carried on the wind from beyond the woods?

Stella and Tom soon discover that they have travelled back in time to their home and its gardens almost 100 years earlier. Here they make both friends and enemies, and uncover startling connections between the past and present.