Until Forever by Johanna Lindsey
Beautiful but prim history professor Roseleen White cherished her new precious possession - a thousand-year old Scandinavian sword. Little did she realise that a careless caress of the sword's mighty hilt would conjure up no less a figure than the mighty Thorn Blooddrinker, a Viking warrior who was to fulfil Roseleen's every desire.
Thorn had been the prisoner of a centuries-old curse, and now finds himself enslaved to a woman from an age very different from his own. Yet Roseleen is the true prisoner, held willing captive by a handsome barbarian who sweeps her back to the ancient past on a journey of sensual discovery. Only by banishing him from her life forever can Roseleen free Thorn from his enslavement - forcing her to make a devastating choice that will either emperil their future or preserve a love which will remain powerful... until forever.