Sacred Hearts — Alison Joseph

Nuns are supposed to put worldly concerns behind them when they take their vows, but in the past fifteen years, Sister Agnes has not once forgotten Hugo, her abusive ex-husband. Even after having experienced his viciousness and his violence first-hand, however, Agnes is convinced that Hugo did not murder his second wife.
The police disagree, prompting Sister Agnes's first investigation, one which pulls her into the monied circles of rural Gloucestershire as well as into the lives of the dispossessed - homeless local youth whose fierce friendships may hold the key to the murder.
Will Sister Agnes discover the murderer's identity, or does she already know him...?