Mystery of the night watchers

May, 1910. As the blazing Halley's comet draws close to the earth, Nancy is uprooted to start a new life in Suffolk with a grandfather she has never met. With every curtain drawn shut, Nancy is forbidden from leaving her grandfather's house: no one must know that her or her mother are there. Yet, when Nancy discovers the house's secret observatory, she watches her mother and grandfather creep out every night. Where are they going? And why mustn't any of them be seen? As the mysteries pile up, Nancy has to bring dark secrets from the past to light - even if doing so will put her own life at risk.