Boston has always been a town of baseball fanatics, and the Rizzoli clan is no exception. As the Rizzolis and Maura cheer their team on from the living room sofa, a knock on the door announces a startling arrival. Jane's errant brother, Tommy, is at long last home from prison - and moving into Maura's guest cottage with Angela. Jane sees disaster ahead as she wonders whether her lovable screw-up of a brother will be behave and whether Maura has any idea of the trouble Tommy might cause.
Maura's ringing phone cuts off the debate. A coach from the Pilgrims baseball team has just been found dead in the locker room shower. It's time for Jane and Maura to go to work.
Ron McKenna's death looks at first like an accidental slip-and-fall against the shower head. But the ever-alert Maura is troubled by the state of advanced rigor mortis and the victim's two skull fractures. This is not an accident, she decides, but a homicide. When the murder weapon is identified as a baseball bat, the list of suspects reads like a who's who of local baseball fame, including the battling husband-and-wife team owners, the Pilgrims' security chief and superstar athlete Manny Vega, whose addictions threatened to bring down the team.
As Maura and Jane use forensics and street smarts to track down the coach killer, Maura becomes a crime victim herself when her house is cleaned out by a burglar. Now Jane has two perps to deal with - and one of them may be her own brother Tommy.