Touch Like Breathing by Theda Black

Facing life and death situations as cops shouldn't be easier than facing each other … should it? Will and Tyler lost each other after Anna's death, but they’re determined to save their friendship and partnership on the force. Good thing they’re determined—it's going to take everything they've got as the pressure mounts and denial, anger and pain drives one of them to do something he’ll never forgive himself for. Luckily his best friend has enough forgiveness for both of them—at least until he disappears, leaving behind a grieving partner who’ll do absolutely anything to save him.