Former serial killer Byung Soo gets diagnosed with Alzheimer's. The doctor tells him that it's due to the aftereffects of a traffic accident 17 years ago, the same accident that stopped him from his killings and allowed him to live a normal life with his dear daughter. So when a series of murders occur near his town, Byung Soo gets worried whether the killings are his doing during his memory lapses. But then he comes across Tae Joo and instinctively realizes that he is the serial killer. He reports this to the police. Byung Soo tries to find firm evidence that Tae Joo is a psychopath but only raises Tae Joo's interest in him and his daughter. And now, with his memory slipping, Byung Soo must find a way to protect his daughter from Tae Joo. (Source: ShoeBox) ~~ Adapted from the novel "A Murderer's Guide to Memorization" (살인자의 기억법) by Kim Young Ha (김영하).