Early morning, 1902. At 7/7 Marchmont Crescent, Eilidh the charlady tips coal into a fire grate and sets it alight. Overhearing, Grimalkin the cat ambles over to curl up against the welcome heat and lick his favorite human's hand. But this is to be his last day on earth...before he becomes the Ghost Cat.

Follow Grimalkin as he witnesses the changes of the next 120 years, prowling unseen among the inhabitants of an Edinburgh tenement while unearthing some startling revelations about the mystery of existence, the unstoppable march of time and the true meaning of feline companionship.