The wheels of the great machine turn again… Three years after the destruction of Engn, Finn is awoken by a shattering earthquake. As the people of the valley flee the ruins, rumours circulate that the machinery of Engn is working once more. Finn is haunted by the thought that Connor desperately needed him to do something. Uncovering buried secrets, Finn sees he has to return to the wreckage of Engn to find the answers to his questions. To him, the events of the Clockwork War are history, but he learns that others are still fighting the ancient battle. For them, the machinery of Engn and its mysterious purpose are at the heart of everything. Diane refuses to come with him, thinking he needs to put the past behind him. But then Engn's line-of-sight signals start to broadcast again…