Gone in the Night by Joanna Schaffhausen
Private eye/former cop/pregnant wife Annalisa Vega gets a note from her imprisoned brother that one of his fellow inmates might be innocent and he wants her to look into his case. When she starts looking into the case, she realizes that her cop husband, Nick, might have missed a few clues on the murder case that the inmate was arrested for. And when she refuses to stop looking, it causes a lot of tension between them. But then he realizes she may be onto something and the real killer may still be on the loose. Quite the page turner.