The Door At The Top Of The Stairs by Alison Naomi Holt

Undercover officer Jesse Shaunessy is kidnapped and tortured, then thrown away by her department as damaged goods. The mind is a powerful ally, and 26-year-old Jesse has no memory of the abduction or the subsequent torture. Inevitably, the protective walls carefully constructed by her subconscious are beginning to crumble. Insanity, friendship, and redemption are all possibilities dependent upon one choice, one gamble, and two determined women who must risk everything to save one lost soul.