The Vanishing of Audrey Wilde by Eve Chase 

Apart from one brief scene where someone gets smacked about the head, I’d call this a cosy.
The story follows a young girl Margot in the nineteen-fifties and a woman Jessie in the present day at a house called Applecoat Manor where Margot’s cousin Audrey vanished in nineteen-fifty-four.
Jessie’s step-daughter Bella becomes engrossed in the house’s mystery and her behaviour towards her baby sister takes a sinister turn.
Margot arrives to spend the summer at the house of her aunt and uncle who have not recovered from the disappearance of their daughter, but when two boys from nearby Cornton Hall show an interest in the Wilde sisters, the mystery unravels in the turmoil of young love.
Are the ghosts of Applecoat coming to claim another victim?
What is the enigmatic Harry hiding?
Will Bella be safe sleeping in Audrey’s old room?

To find out, I highly suggest you read the book.