Headstrong journalist Anna Rothman knows what suicide looks like—her own husband killed himself five years earlier. When Elly Swift, an agitated passenger beside her on a train, leaves a locket in Anna's bag before jumping onto the tracks, Anna starts asking awkward questions. But everything points to suicide and the police close the case. Anna, however, believes Elly's fears for Toby, her young nephew, missing since being snatched from St Stephen's church six months ago, fail to explain the true reason behind Elly's distress. Through a series of hidden messages Elly left behind, Anna embarks on a dangerous crusade to track down Toby and find Elly's killer. But nothing is as it seems and Anna opens a can of worms that throws into question even her own husband's suicide—before the threads of the mystery converge in an astonishing conclusion.