A decade ago, Tokyo Police Detective Kyoichiro Kaga went to collect the ashes of his recently deceased mother. Years before, she ran away from her husband and son without explanation or any further contact, only to die alone in an apartment far away, leaving her estranged son with many unanswered questions. Now in Tokyo, Michiko Oshitani is found dead many miles from home. Strangled to death, left in the bare apartment rented under a false name by a man who has disappeared without a trace. Oshitani lived far away in Sendai, with no known connection to Tokyo - and neither her family nor friends have any idea why she would have gone there.