Four-thousand-year-old Berach is your everyday immortal vigilante who wants nothing more than to kill bad guys with her mortal girlfriend, Mattie, in 19th century London. When the villains are vanquished, there's nothing better than bantering with her found family, cuddling with Mattie, and reading the newest Sherlock Holmes serial. It's a good life after breaking up with her narcissistic ex, Scáthach, three thousand years ago.
Unfortunately, what's supposed to be a run-of-the-mill kill spirals out of control when Scáthach shows up and slices Mattie on the cheek with the cursed Blade. It's the very weapon Berach made thousands of years to ensure a painful death within a week of a single cut. No one has ever survived its sharp kiss.
Berach is determined to make Mattie the first survivor, no matter what it takes, for death is the one place Berach can't follow. Saving her will mean turning to other immortals she's pissed off over the centuries and facing the monster Berach keeps on a tight leash inside herself, a beast she swore to never release again because she'll lose her hard fought for humanity. But if saving Mattie's life means losing her own soul and working with her ex again, well-
How messy can one break-up be?