Brother vs. Brother

After answering a call about a prowler, Detective Mare Sheehan shoulders her chief's directive to revive an unsolved missing person's case amid increased community pressure. Later, while her loved ones celebrate her ex-husband Frank's engagement, Mare attends a celebration for her legendary high school basketball win.

Mare questions the suspects in a grisly murder case and gives an icy welcome to Colin Zabel, a county detective called in to assist.​

As Mare and Colin parse new physical evidence, phone records lead to an unlikely suspect. After lashing out at Helen about a possible custody fight over Drew, Mare receives some unprompted advice from Richard on moving forward with Carrie. Later, Kenny and Mare face the consequences of their misguided attempts to protect their families.

With Mare forced to take a backseat on the case, Colin presses a local priest about the vague circumstances that prompted his transfer to the parish. Meanwhile, an anonymous call gives Dawn hope that Katie might still be alive.

Mare opens up about her family's history of mental health struggles in her mandated therapy. Meanwhile, Lori tries to get to the bottom of her son's outburst at school, and later, Mare meets with a semi-retired source to help find a possible connection to her three cases.

After a heroic rescue lands her in the hospital, Mare awakes to the unshakeable pain of losing a friend. Then, given a second chance by Chief Carter, Mare reevaluates old suspects, which leads to a shocking clue. Meanwhile, Richard visits Mare in hopes of deepening their relationship, and Lori confides in her best friend about recent family troubles.

When her investigation takes a series of devastating turns, Mare's friends and family members process the fallout as she finally attempts to find her own way forward.