Fallen follows the story of Luce, a young woman who is sent to a cult-like rehab facility called Sword & Cross to serve time for a crime she can't remember committing. Among the other residents, she encounters the enigmatic Daniel and exasperating but irresistible Cam, all of whom are under the watchful eye of the sinister chief doctor Howson, and devout twin sisters Miriam and Sophia. Luce must untangle the mystery of who she is and why she has a connection to Daniel that goes far back beyond their time in the institution.