Book 3 in The Secret Lake mystery adventure series. When Tom and Stella find a 100-year-old letter from their Edwardian friend Jack, his plea for help leads them and their friend Hannah back down the time tunnel to 1913. There the adventurers reunite with friends Lucy, Emma and Sophie at the grand Penworth Estate – unaware of the danger that awaits. Young heir Sebastian has fallen mysteriously ill, and tensions are running high in the household. With secrets lurking in every shadowy corner, it’s up to the friends to unravel a dangerous mystery that threatens Sebastian’s life. Can the time-travelling detectives expose the truth behind Sebastian’s illness before it’s too late? Will the villain at Penworth succeed with their deadly plans?