Garrow attempts a risky insanity defense on behalf of James Hadfield, who is charged with high treason after trying to assassinate King George III.
Detective Inspector Alex Ridley, who is lured back into service as a consultant detective when his former protégée, Carol Farman, needs help cracking a complex murder case.
《摩斯探长前传》第三季确定于2016年1月在ITV播出。新季将以1967年为背景，剧情承接第二季结尾，依旧由Shaun Evans和Roger Allam联合主演，Russell Lewis担任编剧，摩斯探长系列小说作者Colin Dexter担任顾问。本季四集的标题分别为《旅程》、《桃源》、《狩猎》、《终曲》。