Burning Down the House

Jane and Maura are on the case of a fire fighter killed in a fire. When the death looks suspicious, Maura declares it a murder. When Maura orders the fire reports for the unit, she becomes the next target of the killer. The killer attempts to kill Maura by running her over, but instead Maura's mother pushes her out of the way. With Constance in critical condition, Paddy Doyle comes back to town to protect Maura. Maura tells Jane, who tells Agent Dean, but as her boyfriend, not as an FBI Agent. Jane and Korsak suspect that it's a firefighter who has set the fires, so they inspect all the firefighters. Planning a sting to catch the killer, Jane sends Maura undercover in the building of the fire. When the killer is just about to take a gun and shoot Maura, Paddy shoots him. Jane not seeing this coming runs in, but Agent Dean comes out and shoots at Doyle. Paddy shoots Dean and Jane shoots Paddy. He falls off a platform and hits the ground. The episode ends with Jane and Maura's friendship in pieces and Paddy on the ground dying.