Lydia Sparks is a ditzy young woman who is heavily pregnant when she is befriended by Angela. It is soon revealed that her child is either Angela's son Tommy's or Angela's ex-husband Frank's. Eventually the boy is known as TJ, for Tommy, Jr., once a test confirms that Tommy is his father.
Tommy had introduced Frank to his old girlfriend Lydia, who ended up as Frank's girlfriend and fiancée.
Lydia introduces her fiancé, Stuart "Strawberry" Strawbridge, at Tommy Jr's Baptism. They plan to move to Abilene and Strawberry wants to have his "own kids". This will be possible because Tommy Sr didn't turn in his custody paperwork. The Rizzolis hatch a plan to reunite Lydia and Tommy.
Jane and Maura host a girls' night with Lydia and when Tommy shows up on the pretense of moving a couch, Jane ruins dinner and drags Maura out for takeout. Tommy and Lydia fight and Lydia storms out.
Maura says that they should "get rid" of Strawberry. Jane admits that she ran his name and he has no record.
Maura says that Stuart has severe allergies. Maura and Jane are to babysit T.J. while Lydia and Stuart go to a going-away party, and Tommy comes in with Jane's dog, Jo Friday. It turns out that Stuart is severely allergic to dogs, which ruins Lydia's fantasies of a house full of kids and dogs. Stuart leaves and Lydia and Tommy goes for a walk.