When Tess is forced to rent out her late sister's old room to pay the bills, the urge to rummage through her guests' belongings overtakes her every thought. Teasing herself with forbidden glimpses into the lives of strangers is a momentary thrill, but it's the closest she's felt to anyone since the mysterious death of her sister, Rosie.

After her newest lodger, Arran, takes the room, Tess finds his salaciously detailed diary, which chronicles his infatuation with a beautiful stranger. The diary, which appears harmless at first, slowly takes a darker, more menacing tone with each new entry. Is this a crush or an obsession?

Her compulsion to know the truth leads to Tess shadowing Arran through the streets of London, hoping to catch a glimpse of this unnamed woman. And as she continues to peruse his diary, she can't help but notice the similarities between the woman on the pages and herself.

Tasha Sylva's thrilling debut, perfect for readers of A.J. Finn and Lucy Foley, will keep you asking, Who has truly been watching whom?