After all that they've been through, no one would deny that Hart and Drake deserve a happily-ever-after life together. But, on the eve of their Christmas wedding, a threat long buried returns to threaten them. Not just their happiness, not only their lives, but everything they hold dear. Separated and desperate to save each other, untangling a knot of mystery dating back to Hart's Gram Rosa's fight against the Nazis, and facing an enemy unlike any they've encountered before, both must search their hearts to find the strength to survive. Meet the ER doctor who never quits--and the detective who will never give up on the love they share. An unforgettable finale for an unforgettable couple who prove that two wounded souls have the power to save each other.