Professor David Ash is invited to Edbrook to calm the fears of the elderly nanny of the Mariell family. Nanny Tess is seeing things, and Ash’s book debunking such phenomenon makes him a good choice to set her mind at ease and convince her she is just tired and stressed. But soon after arriving David too begins to doubt his senses, and watching the odd behavior of the three grown Mariell children doesn't make his task any easier.