CUCKOO by Julia Crouch

A dark, juicy, deliciously unsettling, read-it-in-one-sitting psychological drama.
Rose has it all - the gorgeous children, the husband, the beautiful home. But then her best friend Polly comes to stay. Very soon, Rose's cosy world starts to fall apart at the seams - her baby falls dangerously ill, her husband is distracted - is Polly behind it all? It appears that once you invite Polly into your home, it's very difficult to get her out again...
I found the description of this book intriguing. ...