The Awkward Squad by Sophie Hénaff

Suspended from her job as a promising police officer for firing "one bullet too many", Anne Capestan is expecting the worst when she is summoned to H.Q. to learn her fate. Instead, she is surprised to be told that she will head up a new police squad, working on solving old cold cases.

Though relieved to have a job still, Capestan is not overjoyed by the prospect of her new role. Even less so when she meets her new team: a crowd of misfits, troublemakers and problem cases, none of whom are fit for purpose and yet none of whom can be fired.

But from this inauspicious start, investigating the cold cases throws up several strange mysteries for Capestan and her team: was the old lady murdered seven years ago really just the victim of a botched robbery? Who was behind the dead sailor discovered in the Seine with three gunshot wounds? And why does there seem to be a curious link with a ferry that was shipwrecked off the Florida coast many years previously?