Trespasser by Tana French
This is the case she imagined. Precision-cut and savage, lithe and momentous. Antoinette Conway, the tough, abrasive detective from The Secret Place, is still on the Murder squad, but only just.
She's partnered up with Stephen Moran now, and that's going well - but the rest of her working life isn't. Antoinette doesn't play well with others, and there's a vicious running campaign in the squad to get rid of her. She and Stephen pull a case that at first looks like a slam-dunk lovers' tiff.
All she and her partner have to do is track down Lover Boy and bring him in. Then it'll be back to business as usual, watching from a distance as the real detectives go up against the psychopaths. Except when Antoinette takes a good look at the victim's face, she realises she's seen her somewhere before.
And suddenly the conviction that there's a different answer takes her breath away.