Chase is based on two detectives, Shounosuke Nanase and Koto Amekura, that are tipped off by an anonymous caller that an explosion five years prior, previously ruled an accident, was purposely set off to mask a murder, leading to a new investigation of the case. Source: Wikipedia, "[en.wikipedia.org/wiki/Chase%3A_Cold_Case_Investigations_-_Distant_Memories Chase: Cold Case Investigations - Distant Memories]", available under the CC-BY-SA License.