Tasked by the queen to close the 'Septimus Wave' case once and for all, Captain Blake is facing a daunting task, for many questions remain unanswered. Where did the spaceship buried beneath London come from? What became of Lady Rowana and Professor Evangely? Meanwhile, Mortimer is trying to pull Olrik out of the catatonic state the villain has been in since his encounter with the ship's occupant. Has the threat to the nation truly been vanquished?