Ripple Effect

As Danny and Lena follow a promising lead in the attack on Detective Rodgers with the help of her father, they find themselves in an intense standoff with a dangerous biker gang. Meanwhile, Mae faces renewed pressure from political rival Thad Longfellow, Sean and Jonah attempt to make amends after a misstep at work and Baez is confronted with an unexpected family matter.

Fire in the Hole

When a subway station shootout leaves a detective critically injured, Danny and Lena race to determine what really happened; Sean grapples with how police work affects those closest to him.

Everything Right Can Still Be Wrong

When human remains are discovered inside a great white shark, Danny and Lena find themselves hunting a killer. Meanwhile, Sarah reopens a troubling case from her past and Sean and Jonah get caught in the middle of a neighborhood feud.

Blood Diamonds

Jamie Reagan's visit to Boston takes an unexpected turn when he and Danny are drawn into a diamond heist linked to a violent family feud, forcing the brothers to confront lingering tensions of their own. Meanwhile, Mae faces a difficult case after swatting results in a man's death, Lena investigates a series of suspicious deaths linked to one of Reverend Peters' parishioners and Sarah and Seth encounter an unexpected hurdle while planning their wedding.

Bloodlines

When Boston P.D. discovers a baby abandoned in a food delivery robot, Danny's anger causes him to slip back into his old rule-breaking ways. Also, Sarah faces a difficult decision when her estranged mother, Gwen (Marg Helgenberger), reenters her life, and Sean and Jonah search for a fellow officer who went AWOL.

Crisis