The Good Turn by Dervla McTiernan

The unputdownable new novel from the bestselling author of The Ruin and The Scholar.
Sometimes to fix the law you have to break it...
Police corruption, an investigation that ends in tragedy and the mystery of a little girl's silence - three unconnected events that will prove to be linked by one small town.
While Detective Cormac Reilly faces enemies at work and trouble in his personal life, Garda Peter Fisher is relocated out of Galway with the threat of prosecution hanging over his head. But even that is not as terrible as having to work for his overbearing father, the local copper for the pretty seaside town of Roundstone.
For some, like Anna and her young daughter Tilly, Roundstone is a refuge from trauma. But even this village on the edge of the sea isn't far enough to escape from the shadows of evil men.