Episode 6x02

Dean, Lisa, and Ben have moved to a new house after the incident with the Djinn in 6.01 Exile On Main St. Dean is hypervigilant to danger and doesn't want Ben or Lisa to leave the house; however, he doesn't want their lives to be the same as his was raised by John, and he yells at Ben for wanting to learn how to shoot a gun. Lisa wants to know what's really gotten Dean so upset. She asks him what he's afraid of, if there's a monster they should be looking out for, but he just says that he's not sure and that anything could come after them given his past. He wants to keep her and Ben safe, but Lisa says that they need to set some parameters so that they can live their lives.

Meanwhile, Sam questions local law enforcement about a husband and wife who have been brutally murdered and their baby, who is missing. As he leaves the crime scene, Sam notices that the family has the same security system as the other families that were killed: Harper Caine Security. Because none of the family's alarm systems went off when they were attacked, he calls Samuel Campbell, who finds one more family with Harper Caine Security that has a young baby and is still "walking and talking." Sam heads to their house, but he's too late. He finds the husband and wife dead in the living room, and the perpetrator still in the house. They fight, and Sam slices his arm with a Silver knife. The wound hisses and burns, but before he can do anything else, the perpetrator flees. Sam hears something in the other room and finds the baby still alive.

Sam calls Dean, who meets him reluctantly but agrees to help after seeing the baby. Before he leaves home he teaches Lisa how to handle a gun.

Sam and Dean stop at a market for baby supplies. Dean reveals he's had some experience with Lisa's infant niece. When they reach the checkout lane, the baby won't stop crying. A woman approaches them and offers help but Dean sees her eyes flash in the security camera feed - she is a Shapeshifter! She tries to take the baby, but Sam and Dean manage to fend her off and escape. The Shapeshifter sees their license plate numbers as they leave and quickly takes the form of a police officer so that it can track them down.

Sam and Dean hole up in a motel room with the baby. Dean says that he's had to be better father material since he started helping Lisa take care of Ben. Sam is skeptical about Dean's resolve to give Ben a better childhood than they had, though, because "moving them around and keeping them on lockdown" isn't any different from how John raised them.

Sam discovers that one of the fathers of a kidnapped baby is still alive and goes to interview him. He learns that the man left his wife, now deceased, because she claimed that she had been impregnated by him even though he was out of town at the time. Sam calls Dean, who is enjoying the motel bed's Magic Fingers, with the theory that the baby is the child of a shapeshifter just as Dean sees skin and blood explode up the wall from the baby's crib. The baby has shifted into the form of the baby it sees on its box of diapers. The baby is still crying from its transformation when the Shapeshifter, in the form of the police officer, breaks into the room. The Shapeshifter says that the baby needs to be with not only its father, but with "our father." Sam enters the motel room and shoots the Shapeshifter through the heart, killing it, and they drive to the Campbells' compound. Despite Dean's misgivings about giving the baby to hunters, Samuel gives the baby to Christian Campbell to raise with his wife, Arlene.

Another Shapeshifter shows up, this time in the guise of Samuel, and demands the return of the baby. A fight ensues, but the creature is immune to bullets, a knife to the heart, and all the tranquilizers they load into it. It kills Mark Campbell and then battles Sam and Dean and takes the baby.

Samuel and Sam speculate that the Shapeshifter was an Alpha. Dean asks Sam if he knew the Alpha was out there and if he purposefully used the baby as bait to bring the Alpha to them. Sam denies it. After they leave, Samuel talks on the phone to someone who apparently wants him to catch the Alpha Shapeshifter and bring it to him.

Dean and Lisa have a final confrontation about what Dean should do, leave them or stay. He wants to do what is safest and best for them. Lisa tells him that she doesn't know what is safer, but that Dean is a hunter and that he needs to stop denying it. She tells him that he can come back when he can, but that he needs to leave. The last scene shows Dean uncovering the Impala and smiling.

Source Super-wiki