Detective Kate Snow and Detective Ally Emerson are headed to Scotland-but this trip is far from a holiday.

With the investigation into Ally's late husband, the notorious criminal Cameron Emerson, finally closed, both women are attempting to breathe again. But peace is short-lived when Kate receives devastating news: her brother Billy has vanished. With a long history of drug addiction and months of silence behind him, Billy's disappearance raises fears that something has gone terribly wrong.

Taking time away from Evergreen Police Department, Kate and Ally travel to Scotland to search for answers unofficially. Their journey leads them to a remote cabin and a trail of half-truths, broken connections, and unsettling discoveries. As they dig deeper, it becomes clear that Billy has become entangled in something far more dangerous than either of them anticipated.

While the search grows increasingly urgent, so too does the bond between Kate and Ally. Away from the pressures of the job, their connection deepens-tested by fear, uncertainty, and the emotional weight of what they are uncovering. What began as trust is fast becoming something neither woman can ignore.

Can Kate and Ally uncover the truth behind Billy's disappearance before it's too late? And amid the danger and darkness, can they allow themselves the promise of something real?

Find out in Blood Promise.