The second season picks up where the first left off, with Anne-Marie Duff (Bad Sisters, The Salisbury Poisonings) returning as Dr Susannah Newman, now on a desperate quest to track down a self-confessed serial killer before he kills again that night. When a mysterious new client Jon (Dominic Cooper) admits under hypnosis that he is a murderer and intends on killing another young female that evening, Susannah knows he must be stopped at all costs. When he escapes before the police arrive and as her former lover Detective Superintendent Richard Grove (Ben Miller; Professor T, Paddington 2) is refusing to take action, Susannah is forced to embark on her own deadly mission to save Sapphire’s life, the way she couldn’t do with her own daughter.

影片改编自日本推理作家东野圭吾的代表作《嫌疑人X的献身》，原名《完美的爱情》，后仍改为和原著接近的《嫌疑人X》。 沉默寡言的天才数学家金石固（柳承范 饰）每天唯一的乐趣，便是去固定的便当店买午餐，只为看一眼在便当店做事的邻居白花善（李瑶媛 饰）。花善与外甥女允儿相依为命，过 着平静的生活，可是有一个总来找麻烦的前夫金哲民。终于有一天，花善因不堪忍受虐待，最终手刃了前来纠缠的前夫。石固察觉花善出于自卫而杀人的事实后，主动提出由他料理善后，为此这桩犯罪设计完美的不在场的证明，保证让花善和允儿不受到牵连。负责查办此案的郑警官（赵镇雄 饰）是石固的好友对花善的凶手身份确认不疑，虽然没有确凿证据，却依然执著地展开调查。 到底石固使用了怎样的隐藏手法？最终他会为爱献身吗？