On the one-year anniversary of Bridget Shiel’s brutal murder, with no progress on finding her killer, Lowe organizes a vigil and canvass to try and generate new leads and give her family some resolution. A tip leads detectives on a wild hunt to try and find her killer. The best evidence they have is the hope of getting a DNA match. Meanwhile, Det. Zimbrick gets a DNA match on a 16-year-old cold case. He and Quinn head to San Francisco where the suspect is incarcerated and get a series of extraordinarily lucky breaks along the way.