Jules and Holly have been best friends since university. They tell each other everything – trading revelations and confessions, and sharing both the big moments and the small details of their lives: Holly is the only person who knows about Jules' affair; Jules was there for Holly when her husband died. And their two children – just four years apart – have grown up together.
So when Jules' daughter Saffie accuses Holly's son of a terrible crime, neither woman can possibly be prepared for what this means – for their families or their friendship.
Especially as Holly refuses to believe her son is guilty.
For fans of He Said, She Said and Anatomy of a Scandal, Penny Hancock's I Thought I Knew You is about secrets and lies – and whose side you take when it really matters.