|In Manning, Colorado, a man named Daniel Elkins is sitting in a bar, reading through notes in a journal very similar to that of John Winchester. He hears a noise behind him and watches as three men and a woman walk in. Realizing who they are, he runs off, driving back home to his cabin as quickly as possible. He frantically tries to get to a gun locked in his safe but he comes face to face with Kate, the female from the bar. He loads up the gun, hoping to shoot her before she attacks, but he is too late. Her friends join in and he is killed before he has a chance to use the gun.
Sam and Dean, searching for supernatural occurances to investigate, read about Daniel's death. Dean recognizes the name as being in John's journal - someone that John obviously knows - so they decide to head out to Colorado. They arrive at the cabin, which is completely wrecked, and discover a number scratched into the floor. It's a sequence of digits that leads them to a mail box in which they find a letter addresses to J.W. Sitting in the car, they wonder if this could be for their father when someone knocks on the window - it's John himself. The letter reveals that Daniel had a gun John previously believed to be a myth. John needs that gun and knows he has to track down the creatures that stole it and killed Daniel. Sam and Dean don't believe at first when John explains that it's vampires they are chasing after, but he soon reveals that despite most vampire lore being wrong, they certainly do exist.
John hears on a police scanner that a couple are missing and their car has been found. He believes that this is the vampires and the three of them go to investigate. In the vampire lair, the couple who went missing are still alive, but are tied up and being taunted by the vampires. Kate shows Luther, the leader of the group, the gun that she stole from Daniel. Luther worries about this as he knows that there are other hunters out there who will track them down in revenge for her killing Daniel. Sam gets more and more irritated at John ordering them about and finally snaps. He confronts his father, both of them saying some harsh words, until Dean comes between them and calms them down.
The next day, the three of them are staking out the vampire lair. John reveals why the gun is so important - it can kill anything, supernatural or otherwise and he wants it to destroy the demon when he finally tracks it down. They head inside to where the vampires are sleeping. Sam sees the woman who went missing and tries to free her, but she wakes up, revealing that she is now a vampire herself and the Winchesters run for their lives. John sends Dean out to a funeral home to collect some blood from a corpse, while Sam reconciles his differences with his father - the pair of them finally acknowledging that they have a lot more in common than most people. John explains that the reason he was so angry when Sam went off to college was because he knew he wouldn't be able to protect him anymore.
That night, their plan goes to work. Kate tracks them down and attacks Dean, but she is shot by a crossbow bolt covered in the blood of a dead man - something which acts as a poison on vampires. She collapses in their arms and the other vampire she was with is beheaded. The plan is to offer her back to Luther in exchange for the gun. While Sam and Dean clean out the remaining vampires from the lair, John faces off against Luther. His plan backfires when Kate manages to break free. John is about to be killed when Sam and Dean arrive and join the fight. When Sam is captured by Luther, John uses one of the Colt's precious bullets to kill Luther. Back in the motel, John tells the boys off for ignoring his direct order to stay away, but they remind him that they saved his life. He finally agrees that they work better as a team and they decide to go after the demon together as a family.