This chapter explains the technological infrastructure of Nocturnal within the context of sensing and actuation used in ambient assistive living (AAL), highlights the peculiarities of assisting people in the hours of darkness, and focuses on the consequences to society of the AAL-associated technology. People with dementia may have a much more pronounced and immediate need for help and support as they awake in an unknown, dark environment. Nocturnal can be set up to monitor every room within the home of the person with dementia. Important requirements for nocturnal care of people with dementia are more specialized algorithms to infer behaviour from sparse data; specially designed interventions, perhaps including music and video, that provide therapeutic support to people to reduce anxiety; and sophisticated guidance, perhaps through the use of lightning. There is a significant body of research that has described the needs of people with dementia and has produced solutions to address those needs using information and communication technologies.